CARRIER HANDBOOK OF AIR CONDITIONING SYSTEM DESIGN PDF
Carrier - Handbook of Air Conditioning System Design (Part 1) - Free ebook download as PDF File .pdf), Text File .txt) or read book online for free. Carrier Handbook of Air Conditioning System Design - Ebook download as PDF File .pdf), Text File .txt) or read book online. and led the design of the HVAC&R systems for Queen Elizabeth Desiccant- based air conditioning systems replace part of the frigeration (HVAC&R), was first systematically developed by Dr. Willis H. Carrier in the early.
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Author: Carrier Air Conditioning Company Air Conditioning System Design Manual, Second Edition Handbook of air conditioning and refrigeration. Design Guide for Heating, Ventilating, and Air Conditioning Systems. February 29, – Last Rev: September 21, i. Table of Contents. Page. Handbook of Air Conditioning System Design [Carrier Air Conditioning Company] on resourceone.info *FREE* shipping on qualifying offers. Book by Carrier Air.
JO Il.. IJilC; l TURE The solid curve i!! Assume 'mat the maximum cooling capuity available is represented by A, and that the capacity is controlled to maintain a constant temperature at partial load. When the actual c. This operates in a similar manner with different periods of operation and with different types of construcriorr, NOTE: The magnitude of the storage effect is determined largrdy by the' thermal capacity or heat holdLo: TM,s "eduction is "0 be faken GI tilt.
Iil'1le of peak looa only. U lAO UI 1. X to"tlred ire",p Swl! It is u. Load paltenu. For iru,r. An interior zone has a. Use ofT,oble 13 - Storoge Fagan. This reducnun is to' be subtracted from "lhe room sensible heal. The sa lUe room 'I! J, flllgr1l!. The peal! Fen uJlllpniscn Imnposn. J1COIl5 h! In this, situation, the eeellng unit lIbl! Jlts off and there is no' cooling during the period Q,f warmillS up. H any pTecooling. Precooling is.
Cul in reducing tbe cooling load in applications su h as chuTches, supermarkeu. In addition f lights being oft: Expanding this to oru: ILer than ""im office build. VII ,jO to. YO Offlu ApCl """'.! IlY pan. The find factor mwt nel: I in]1 bt LJ;;ued 11 I Il: Io IIJpp. JJl1Y ;roo. U alr ii!. S I llm,! HlIJ by bram;.
Ii 0[' sllmcturc: The amoum of solalf heat outslde the earth's, aunosphere vartes bet The solar heat reaching theearth's surra! The seatrered tIldialionis termed di. L The distance eraveled through the atmosphere to reach he point , The an'l. The solar heal gain ilirolllg: Ordinary gias!
I S, p"gs. The toLal sclar heat gain to the conditioned spaceeensistscf rhe rransrniued heat p u: BR4 R or. BiI R J UV Gt NG Heu Gili'1 10 Spil. R Gi'. JI,T R. The inside! II '1'1: H lilt' n. Lhe Ip1I E. Iil1g ,hI! I or he.. I,lIano "'! J relllpero. IIK conditioru: Thi is, t pkal Ior wood wj!. Plecipitable 'water v:: Rooms lO. This is because the dlfhi C cnmpooe'nL increases with increasing haze, as I":. C wiLh 2 '0pfflii;11CS i. North l. Sui III ion: Fnnn TIIM,. Lo- Novnnl"ct 21, 2: JLnJl I'!
I I "cl. GivC n: Ilgn dew'point - By impet;1.! TaMe r. South 0 6 12 13 14 14 Il , 12 ' 6 0 Narth I Southw. APR 20 w. SEPT 22 bit I" b. North 0 6 II 13 J. NOV 21 E. I Sol.. No Sash D. I North I M7 97 31 I HoriJont. I' , HCM'izonfal 0 17 62 fl'l 1. J4- 74 SO 0 Harth. JUNE 21 South Of Jan. V IUi! U - Monthlv Milximums 80tlld V.. North , SaLlthw! Wid 3 8' 1.
FE' 20 '5r.! IS3 11'i8' 22! I, NortI! III i 93 76 I 50 21 0 Narf: SZ' South 0 28 I b' 1'3b I 1]1 ! Eut ' 0 56 Q b i t: II 12 Il' 14 'S5 ' Saar "". Il '14 ''I 14 '14 '14 13 14 20 2. Ellrl JAN 21 South III '? Souihwest HarQo. AUG 2. PT 22 En! FEB 2. JULY B5 or 1. Velues - Monthly MOlimums eo. H sash area Time of Year Time ofY.. MAY 21 North Notth.. I hit Southut So..
South South.. North N B 10 12 S 0 Horilont. R Fie. CIDE 'et: May be thicker, or 2.
May be specially treated to absorb olar heal heat absorbing glass. These special glass types reduce the transmitted solar heat but increase the amount of absorbed solar heat flowing into the space. Normally they reflect lightly less than ordinary gla because pan of the relic tion takes pia e on the inside surface, A portion of heat rell led rom the inside surface is absorbed in passing back through 'the glass. The overall effect, however, is to reduce the solar heat gain to the conditioned space as shown in Fig.
Refer to Item 8, page 5 J, rOI" ab orptivity, rellect1vily ami transmissibility of common types or glass at 30'" angle of incidence. This multiplier. Multipliers for various t pes of glass are listed in Table The effectiveness of a shading device depends on its ability to keep solar heat from the conditioued space.
All shading devices reflect and absorb a major portion of rhesolar gain, leaving a small portion to he transmitted. The outdoor shading devices are much more effective than the inside devices because all of the reflected solar heat is kept out and the absorbed heat is dissipated to the outdoor air.
Refer LO Item 8, pllge - J, or absorptivity, reflectivity and transmissibility of common shading devices at angle of incidence. The solar heat gain rhru glass with an inside shading device' may be expressed as follows: BtuI hr sq ttl. The solar heat gain factor thru the -: Outdoor ennvus: Th avera nil "pI; ; Wlth g,nod' Wilhoyt Shodin,g Device.
Ani inside m og! It re to be used ilppllir. Above the ;Joe aflF: A II sha. I id Ulil 10 the fil I p: The tin. III C'1I1l1: SrI hlll"o: Jin FOld.. I5 "" O 'c'lIlTii'igat 4: July 2: Apply fadors, toTable 15 'Q,uldoor wind ve'loc: Ab[orbifl9 '1'8 to So. NE Ori: IS , T7II1 Examp' 5 - ApI' Oi. Pipf'" " IhIH. Ies i dh ' I 20''';. Rluj tar hI deft Fl, the' rul t'.
J"ly 73 Solo: H 2,0' 3. III, 6: J UW Ui7 Clio O. Ol ncOi'! Oi'it ftf I oliO PIo1 allp; '. This is pril11;1fdly;tu 'd by rhe thcllII. IY the H gain because most If th", lH'al I eflc: B5 multiplier in T lbl;: Lh hllllmll: IJblr n.
II,, H No"" Su"' J X. Solar hnt aaln 'Ii"! I hOun. This h. The 'haded portion has only the diffuse ornpon ni 51Tiking it. Th shading oj d window b , hon- lonro. Overhangs" Fins and Ad. Desermine the olar iUim! Jdl and Itil d ' an- 81 from TaMI! Lo ale [he olar azimuth all' I on the Sail upper part of Clum I. Pro eed horizontaHy to ure exposure desired. Jltilply the d p: Tom Imersecrlon. LO he air cumlitioned, Sol urlon: From Cl! ShadIng by tl c reveal M2 p. From Tn. Refer to. North Ladtude.
From Table , ,. Shading br reveal Slulding hy ""crOang! A , I 1,21 "11,,24 s. II 15! IS, J 42 U;], K l: IQi ,K! IIi S '1 I 19 II Ol IJ! I'll I: ZS9 B 2"1'2 7 21'! I PIlI'! ICI 21t!! II 47 , ' ". G 5: Ni 3D' 1'80 Qr d mining and pr Vtnu 8 'tel' ". He 't Hows from one po'iInt to anoth r whemlve lempenturedi. It is' I. J'i di -: L adon of lh buOdrn blilltude. Tbe b at.
Qtt r 1rt! Whn the sun shines on lhJ w. This r. Cs the le. The heat Bow into til se-ond' Uc-. For mil, pani. Ja waU. J Vv FIG. AT DIl11I. Because each slice must absorb seme he. These dl'agrnms do! R' FIC. IS I'! III vvv. OF A 1lO1J. This same process occurs whh a n. The thermal capacity of a wall or tool is lhl:!
Tbit progressiOP of heat gain lD the. There ore. I' and 20 - Equlwa: Outdoor daily range of -bu'lb cempu21lll! Mwmum outdoor temperalUlte of 9,5 F db and design i'Qdoor tempcrat!. Dark, color ""allJ and roobwitlll absorptivity of 0. Fo light color. UR time. A fbI roof' cxpolCdllllJ the. I", in. Iloom dcslp IEmpmllUre: Equlvalml l. Sol doOn: Cori"tdjQ" A.
UiUl as dq f. TM amatkml co be appl to llx leqWYdmt l pt'B1! L1'lC dilhra! F Dall" nnp: U a nJQf r. Thb eqllJmcPl tempenlun: Thil eq: Rdu 1. I alUS be made: North latitude. Slwall ;: J9 - JIll fl. II 7' 6'.. Table The tolTt'cdon far diffen: July and. U 19', ill: I C';lmll kI Thl 00I'fI! JOdi C1tul1lalml tempt: I' dfi desired. K 1a;t hell. Will or mof dctiRd. Hgtu lllue. The comhined tOl1loul care: Light oolor w,illls f'lr moJ R.
U'C v;Jua from T4bf. Th rare times the temperature dilfc: The reciprocal of the U value Ier ,UlY w: TabltJ Batis of lablft 21 Jhrlll3 - Tramlmillion CooflkLnt. U fOf Wan" Roof,. The difference between summer and winter transmission wefiu: For example.
Outdoor film thermal resistance wint! Thermal resistance of wall without outdoor air film winleT Ma50n'l1' panitIion made If i! Transmission crn: Ml1Id plu e. Rdeflo Table'S 22 l1fld JI. U value tor wall without i. F PART!. II "bI". J Y,h Sond I!. U '6 Ii [ A'I' flU ; Impl "rew cdclilion of inwlatlon AII nu.. H l",dlc,,1e Wlli,,1i1 per. Wood ".. II Pltlclt I " IS -- H:.
I ". U WI All! I I INJ.: AIIg II It LCiifJJ ' II 13tll. IOJ' c. III WI " Ii' I'IIR".
Iwjhr U ",,,lue X r outdoQr I. B I "', tVaht.. C-II wiI'h cilklr! Of IlMor..
W'hwI ' DI llielM. IIAl MilA' ". JI 1'. U ,IOf. IS "". W '11 'f CIt","" EquQ IU " II M'" M N Lwth or N. AI I" "-, liiIkIlna rap. Ii" W Ioard ta I: Gyp Yt W' 1Nul1l11nll hard 2. II I'''''s. I' X leq"h'oh,rjl '. G' Gain 0If Loll. I'flllhr-" Ar I '"til. IS loth. I ,'. QW oynUM 3 SUM lVi. Gypt"In 8 nI ; " Pladwrm I'IQoI. Iliff or wfftor I. In N TIl II -". DI" Pla.. Ill s I Alii. OS , HI ,n. I11I,- H',.. K PRT Ii. Btul hr I Illd l pap.! XI II I Ildll pGper O! R" SIiI. N 20lL Wllhtlt!
Heat ,10,. P',ijlltj' I.. Th rn. I IUU: SooMI All' " 1. U , I rIll I. AI -'2. J15 ,M. AQ- J'O. It W' U WI' loft 1 1' I , Al1I r6 6A. IS J'2. J4I ;J7. It' ",. U,I, "lOw. UI ttl X I,' f. Till ,,,"W. IW, S"..
Til" Til'. T9i- J! LI Wt A! Hut Guoln. Hy '"'. Dlrectioro of H.. Hall af "'. Wint", Added I OM! Two Ad"d On.. In air in air Aiii' I.. I Iliac. Beth II U ; ASS II Air I,.. O,5;S O.. CI ft. Add th. A wan at pet. I MGL.. Refer to To. Outdoor uuum. Slone bong, 2 in. SaM 3. ILE 3. Wood fl'bilr' 1ocHd: UI 2'. U UQ t,. Wood, fj, 01" '1",".
CkllI' fit.. I -'45 I,hl AI! II flj.. IIb, "lII'h, Y. M 10M AC sw.. U AlplHiIt OA MAnI: I l'roc! Fiber Wood! Fiber, Mulft. PI,;mld l! COtne" Sheathing 1m pre!!! Pre'-d, fD I"'Drely Appl'Oo. IEOOloi Ho. Wlnler Down WI"t. Imtif I 0. T the floor varies only a. The grQund is a Above the 8 tlevel. This is b cawe the gT6und tftDpennurearound me perimeter "ariel whh the! Basis of T obt. Ute of Til - 35 tf,,1! The peri meier facto I'ts'too ill Ta'bl4! Heir loss alJOY" ground ft: Entire floor.. Hu' IauthtouV" tloor, Ifill"" - ",r.
Handbook of Air Conditioning System Design (Carrier)
NId and! AI groon. IOO'll O. High ratta of circulation will increase the heat transfer rate, For special problems, consult heal transfer reference books. WIth ' Willi "eel PI,. II lu Ihlen Irt"l1 y.
Water v apor HOW8 from high to lower vapor' pf. This proeeas is. The vapor b: It thoula always bE laced mt thlt s. SIlTel to prclIr: Some DE the values for walls, roofs, ere.
Ill 'p db. III I; b. Ull 4 inch eencreee F1nd': If lIIId! I layer hit lroofl'nl -2 jnd;o I coah a. I g;ala olumlftulR paint DouOkll fir [5 pll,1. HEAT A.
S T.. Notlid Unit. Side at Pop. Ifi ptlp. I CQgb! PM t'1 " -ditto 3Q. JQ lb. Cred too1M.
Q fOlrIl,h Wf'f1liCli '! Alumino,," foil on '"pe.. I" d ,f,,,,1 'l'Qp! Ill'ld tb!!! I'I' wb. This condensation occurs 3'[ the point of saturation temperalure and pressure, All water vapor flows thru the structure. To illustrate this..
The t-emperature and vapor pressure gradient decreases approximately as shown by the solid and dashed lines unril condensation begins saturation point , At millpoint, the latent heal of condensation decreases the rate of temperature drop thru the insulation. This il; approximately indicated by the dotted line.
Thill water vapoT may condense on the under! Concealed I;ondensation may cause wood, iron and brickwork to dderiorate and insulatien to lose its insulating value. No great volli: In winter, ventilate the strueture cavities to remove vapor that has entered. Outdoor air ihru vents shielded from earrance of rain and insects O'I:: Condensation may aJl!
Although the transmission across the large glass window peaks at about 3 p. The sum of these loads results in the peak cooling load occurring at about 4 p.
The weight of the materials surrounding the room in Example 1 is Under partial load operation, the room temperature is between 75 F db and 78 F db, or at the thermostat setting 75 F , depending on the load.
This is because the potential temperature swing is increased, thus adding to the amount of heat stored at the time of peak load. Where the space is precooled to a lower temperature and the control point is reset upward to a comfortable condition when the occupants arrive, no additional storage occurs. In this situation, the cooling unit shuts off and there is no cooling during the period of warming up.
When the cooling unit begins to supply cooling again, the cooling load is approximately up to the point it would have been without any precooling. Precooling is very useful in reducing the cooling load in applications such as churches, supermarkets,.
Diversity of cooling load results from the probable non-occurrence of part of the cooling load on a design day. Diversity factors are applied to the refrigeration capacity in large air conditioning systems. These factors vary with location, type and size of the application, and are based entirely on the judgment of the engineer.
Generally, diversity factors can be applied to people and light loads in large multi-story office, hotel or apartment buildings.
The possibility of having all of the people present in the building and all of the lights operating at the time of peak load are slight. Normally, in large office buildings, some people will be away from the office on other business. Also, the lighting arrangement will frequently be such that the lights in the vacant offices will not be on. In addition to lights being off because the people are not present, the normal maintenance procedure in large office buildings usually results in some lights being inoperative.
Therefore, a diversity factor on the people and light loads should be applied for selecting the proper size refrigeration equipment. The size of the diversity factor depends on the size of the building and the engineers judgment of the circumstances involved. For example, the diversity factor on a single small office with 1 or 2 people is 1.
A building with predominantly sales offices would have many people out in the normal course of business. This same concept applies to apartments and hotels.
Normally, very few people are present at the time the solar and transmission loads are peaking, and the lights are normally turned on only after sundown. Therefore, in apartments and hotels, the diversity factor can be much greater than with office buildings.
These reductions in cooling load are real and should be made where applicable. Table 14 lists some typical diversity factors, based on judgment and experience.
Refer to Chapter 7. Use of Table 14 -- Typical Diversity Factors for Large Buildings The diversity factors listed in Table 14 are to be used as a guide in determining a diversity factor for any particular application.
The final factor must necessarily be based on judgment of the effect of the many variables involved. Heat may be stratified in rooms with high ceilings where air is exhausted through the roof or ceiling.
The second situation applies to applications such as office buildings, hotels, and apartments. With both cases, the basic fact that hot air tends to rise makes it possible to stratify load such as convection from the roof, convection from lights, and convection from the upper part of the walls. The convective portion of the roof load. In any room with a high ceiling, a large part of the convection load being released above the supply air stream will stratify at the ceiling or roof level.
Some will be induced into the supply air stream. If air is exhausted through the ceiling or roof, this convection load released abovethe supply air may be subtracted from the air conditioning load. This results in a large reduction in load if the air is to be exhausted.
It is not normally practical to exhaust more air than necessary, as it must be made up by bringing outdoor air through the apparatus. This usually results in a larger increase in load than the reduction realized by exhausting air. Nominally, about a 10 F to 20 F rise in exhaust air temperature may be figured as load reduction if there is enough heat released by convection above the supply air stream.
Hot air stratifies at the ceiling event with no exhaust but rapidly builds up in temperature, and no reduction in load should be taken where air is not exhausted through the ceiling or roof. With suspended ceilings, some of the convective heat from recessed lights flows into the plenum space. Also, the radiant heat within the room sun, lights, people, etc.
These sources of heat increase the temperature of air in the plenum space which causes heat to flow into the underside of the floor structure above. When the ceiling plenum is used as a return air system, some of the return air flows through and over the light fixture, carrying more of the convective heat into the plenum space. Containing heat within the ceiling plenum space tends to flatten both the room and equipment load.
The storage factors for estimating the load with the above conditions are contained in Table The amount of solar heat outside the earths atmosphere varies between these limits throughout the year. The solar heat reaching the earths surface is reduced considerably below these figures because a large part of it is scattered, reflected back out into space, and absorbed by the atmosphere.
The scattered radiation is termed Diffuse or sky radiation, and is more or less evenly distributed over the earths surface because it is nothing more than a reflection from dust particles, water vapor and ozone in the atmosphere. The solar heat that comes directly through the atmosphere is termed direct radiation. The relationship between the total and the direct and diffuse radiation at any point on earth is dependent on the following two factors: The distance traveled through the atmosphere to reach the point on the earth.
The amount of haze in the air. As the distance traveled or the amount of haze increases, the diffuse radiation component increases but the direct component decreases. As either or both of these factors increase, the overall effect is to reduce the total quantity of heat reaching the earths surface.
Ordinary glass is specified as crystal glass of single thickness and single or double strength. The solar heat gain through ordinary glass depends on its location on the earths surface latitude , time of day, time of year, and facing direction of the window. The direct radiation component results in a heat gain to the conditioned space only when the window is in the direct rays of the sun, whereas the diffuse radiation component results in a heat gain, even when the window is not facing the sun.
The amount reflected or transmitted depends on the angle of incidence. The angle of incidence is the angle between the perpendicular to the window surface and the suns rays, Fig. As the angle of incidence increases, more solar heat is reflected and less is transmitted, as shown in Fig. The total solar. The outdoor film coefficient is approximately 2.
Load Estimating Chapter 4. Solar Heat Gain Thru Glass 2. The inside film coefficient is approximately 1. If outdoor temperature is equal to room temperature, the glass temperature is above both.
Therefore absorbed heat. As the outdoor temperature rises, the glass temperature also irises, causing more of the absorbed heat to flow into the space. This reasoning applies equally well when the outdoor temperature is below the room temperature. No haze in the air.
Sea level elevation. A sea level dewpoint temperature of Precipitable water vapor is all of the water vapor in a column of air from sea level to the outer edge of the atmosphere. If these conditions do not apply, use the correction factors at the bottom of each page of Table Use of Table 15 - Solar Heat Gain thru Ordinary Glass The bold face values in Table 15 indicate the maximum solar heat gain for the month for each exposure.
The bold face values that are boxed indicate the yearly maximums for each exposure. Table 15 is used to determine the solar heat gain thru ordinary glass at any time, in any space, zone or building.
To determine the actual cooling load due to the solar heat gain, refer to Chapter 3, Heat Storage, Diversity and Stratification. CAUTION Where Estimation Multi-Exposure Rooms Or Buildings If a haze factor is used on one exposure to determine the peak room or building load, the diffuse component listed for the other exposures must be divided by the haze factor to result in the actual room or building peak load.
This is because the diffuse component increases with increasing haze, as explained on page Basis of Table 15 - Solar heat Gain thru Ordinary Glass Table 15 provides data for 0, 10, 20, 30, 40, and 50 latitudes, for each month of the year and for each hour of the day. This table includes the direct and diffuse radiation and that portion of the heat absorbed in the glass which gets into the space.
It does not include the transmission of heat across the glass caused by a temperature difference between the outdoor and inside air. See Chapter 5 for U values. The data in Table 15 is based on the following conditions: This is typical for wood sash windows. Solar Heat Gain Thru Glass Example 1 Peak Solar Heat Gain 2 Exposures Since the time at which the peak solar load occurs in a space with 2 exposures is not always apparent, the solar heat gain is generally calculated at more than one time to determine its peak.
A room with equal glass areas on the West and South at 40 North latitude. Peak solar heat gain. Bottom Table 15 The conditions on which Table 15 is based do not apply to all locations, since many cities are above sea level, and many have different design dew points and some haze in their atmosphere.
A west exposure with steel casement windows Location Topeka, Kansas Altitude ft Design dewpoint Peak solar heat gain Solution: By inspection of Table 15 The boxed boldface values for peak solar heat gain, occurring at 4: From Table 15 Solar heat gainSeptember 22 2: West 99 1: West 88 South 59 Total Solar heat gainNovember 21 2: West 74 91 South 59 Total The peak solar heat gain to this room occurs at 3: The peak room cooling load does not necessarily occur at the same time as the peak solar heat gain.
Glass, other than ordinary glass, absorbs more solar heat because it 1. May be thicker, or 2. May be specially treated to absorb solar heat heat absorbing glass. These special glass types reduce the transmitted solar heat but increase the amount of absorbed solar heat flowing into the space.
Normally they reflect slightly less than ordinary glass because part of the reflection takes place on the inside surface. A portion of heat reflected from the inside surface is absorbed in passing back through the glass. The overall effect, however, is to reduce the solar heat gain to the conditioned space as shown in Fig. Refer to Item 8, page 51, for absorptivity, reflectivity and transmissibility of common types of glass at 30 angle of incidence.
This multiplier. Multipliers for various types of glass are listed in Table The effectiveness of a shading device depends on its ability to keep solar heat from the conditioned space. All shading devices reflect and absorb a major portion of the solar gain, leaving a small portion to be transmitted. The outdoor shading devices are much more effective than the inside devices because all of the reflected solar heat is kept out and the absorbed heat is dissipated to the outdoor air.
Inside devices necessarily dissipate their absorbed heat within the conditioned space and must also reflect the solar heat. Refer to Item 8, page 51, for absorptivity, reflectivity and transmissibility of common shading devices at 30 angle of incidence. The solar heat gain thru glass with an inside shading device may be expressed as follows: For drapes the above formula changes as follows, caused by the hot air space between glass and drapes: The solar heat gain factor thru the combination in Fig.
Actually the reaction on the solar heat reflected back through the glass from the blind is not always identical tot he first pass as assumed in this example. The first pass through the glass filters out most of solar radiation that is to be absorbed in the glass, and the second pass absorbs somewhat less. For simplicity, the reaction is assumed identical, since the quantities are normally small on the second pass. An outdoor film coefficient of 2. An inside film coefficient of 1.
This is not 1. A 30 angle of incidence which is the angle at which most exposures peak. The 30 angle of incidence is approximately the balance point on reduction of solar heat coming through the atmosphere and the decreased transmissibility of glass.
Carrier Handbook of Air Conditioning System Design
Above the 30 angle the transmissibility of glass decreases, and below the 30 angle the atmosphere absorbs or reflects more. All shading devices fully drawn, except roller shades. Experience indicates that roller shads are seldom fully drawn, so the factors have been slightly increased.
Venetian blind slats horizontal at 45 and shading screen slats horizontal at Outdoor canvas awnings ventilated at sides and top. See Table 16 footnote. Since Table 15 is based on the net solar heat gain thru ordinary glass, all calculated solar heat factors are divided by.
The average absorptivity, reflectivity and transmissability for common glass and shading devices at a 30 angle of incidence along with shading factors appear in the table below.
Use of Table 16 - Over-all Factors for Solar Heat Gain thru Glass, With and Without Shading Devices The factors in Table 16 are multiplied by the values in Table 15 to determine the solar heat gain thru different combinations of glass and shading devices. The correction factors listed under Table 15 are to be used if applicable. Transmission due to temperature difference between the inside and outdoor air must be added to the solar heat gain to determine total gain thru glass.
Occasionally it is necessary to estimate the cooling load in a building where the blinds are not to be fully drawn. The procedure is illustrated in the following example: West exposure, 40 North latitude Thermopane window with white venetian blind on inside, 3 4 drawn.
By inspection of Table 15, the boxed boldface values for peak solar heat gain, occurring at 4: Consult manufacturers for actual values. West exposure, 40 North latitude Solex R glass in steel sash, double hung window. By inspection of Table 15 the boxed boldface value for peak solar heat gain, occurring at 4: Solex R glass absorbs A combination as in Fig. The over-all factor. Figure 17 shows the distribution of solar heat.
These divisions are based on reasoning partially stated in the notes under Fig. These factors can be approximated 1 by using the solar heat gain flow diagrams in Fig. Metal slats 0. For fully drawn roller shades, multiply light colors by.
The 1. At solar altitudes below following table presents the absorption qualities of the most common glass Factors for solar altitude angles of 40 or greater. Use following multipliers: Angle Med. Aklo Blue Ridge Glass Corp. Coolite Mississippi Glass Co.
With multicolor windows, use the predominant color. Commercial shade bronze. The transmission of heat caused by a difference between the inside and outdoor temperatures must also be figured, using the appropriate U value, Chapter 5. West exposure, 40 North latitude Glass block window Find: By inspection of Table 15, the peak solar heat gain occurs on July Glass block differs from sheet glass in that there is an appreciable absorption of solar heat and a fairly long time lag before the heat reaches the inside about 3 hours.
This is primarily caused by the thermal storage capacity of the glass block itself. The high absorption of heat increases the inside surface temperature of the sunlit glass block which may require lower room temperatures to maintain comfort conditions as explained in Chapter 2. Shading devices on the outdoor side of glass block are almost as effective as with any other kind of glass since they keep the heat away from the glass. Shading devices on the inside are not effective in reducing the heat gain because most of the heat reflected is absorbed in the glass block.
Solar heat gain At 4: Use the summer factors for all latitudes, North or South. Use the winter North or South latitude. All windows are shaded to a greater or lesser degree by the projections close to it and by buildings around it. This shading reduces the solar heat gain through these windows by keeping the direct rays of the sun off part of all of the window. The shaded portion has only the diffuse component striking it. Shading of windows is significant in monumental type buildings where the reveal may be large, even at the time of peak solar heat gain.
Chart 1, this chapter, is presented to simplify the determination of the shading of windows by these projections. Basis of Chart 1 - Shading from Reveals, Overhangs, Fins and Adjacent Buildings The location of the sun is defined by the solar azimuth angle and the solar altitude angle as shown in Fig. The solar azimuth angle is the angle in a horizontal plane between North and the vertical plane passing through the sun and the point on earth.
The solar altitude angle is the angle in a vertical plane between the sun and a horizontal plane through a point on earth. The location of the sun with respect to the particular wall facing is defined by the wall solar azimuth angle and the solar altitude angle.
The wall solar azimuth angle is the angle in the horizontal plane between the perpendicular to the wall and the vertical plane passing through the sun and the point on earth. The shading of a window by a vertical projection alongside the window see Fig. The shading of a window by a horizontal projection above the window is the tangent of angle X , a resultant of the combined effects of the altitude angle A and the wall solar azimuth angle B , times the depth of the projection.
Determine the solar azimuth and altitude angles from Table Locate the solar azimuth angle on the scale in upper part of Chart 1. Proceed horizontally to the exposure desired. Drop vertically to Shading from Side scale. Multiply the depth of the projection plan view by the Shading from Side. Locate the solar altitude angle on the scale in lower part of Chart 1. Move horizontally until the Shading from Side value 45 deg. Drop vertically to Shading from Top from intersection. Multiply the depth of the projection elevation view by the Shading from Top.
Example 8-Shading of Window by Reveals Given: A steel casement window on the west side with an 8-inch reveal. Shading by the reveal at 2 p. The same window as in Example 8 with a 2 ft overhang 6 inches above the window. Shading by reveal and overhang a 2 p. Refer to Fig. Buildings located as shown in Fig. Shading at 4 p. It is recommended that the building plans and elevations be sketched to scale with approximate location of the sun, to enable the engineer to visualize the shading conditions.
It also presents data for determining and preventing water vapor condensation on the enclosure surfaces of within the structure materials. Heat flows from one point to another whenever a temperature difference exists between the two points; the direction of flow is always towards the lower temperature.
Water vapor also flows form one point to another whenever a difference in vapor pressure exists between the two points; the direction of flow is towards the point of low vapor pressure. The rate at which the heat or water vapor will flow varies with the resistance to flow between the two points in the material.
If the temperature and vapor pressure of the water vapor correspond to saturation conditions at any point, condensation occurs. This occurs early in the morning after a few hours of very low outdoor temperatures. This approaches steady state heat flow conditions, and for all practical purposes may be assumed as such. Heat flow thru the interior construction floors, ceilings and partitions is caused by a difference in temperature of the air on both sides of the structure.
This temperature difference is essentially constant thru out the day and, therefore, the heat flow can be determined from the steady state heat flow equation, using the actual temperatures on either side. The process of transferring heat thru a wall under indicated unsteady state conditions may be visualized by picturing a inch brick wall sliced into 12 one-inch sections.
Assume that temperatures in each slice are all equal at the beginning, and that the indoor and outdoor temperatures remain constant. When the sun shines on this wall, most of the solar heat is absorbed in the first slice, Fig. This raises the temperature of the first slice above that of the outdoor air and the second slice, causing heat to flow to the outdoor air and also to the second slice, Fig. The amount of heat flowing in either direction depends on the resistance to heat flow within the wall and thru the outdoor air film.
The heat flow into the second slice, in turn, raises its temperature, causing heat to flow into the third slice, Fig.
This process of absorbing heat and passing some on to the next slice continues thru the wall to the last or 12th slice where the remaining heat is transferred to the inside by convection and radiation. For this particular wall, it takes approximately. Heat gain thru the exterior construction walls and roof is normally calculated at the time of greatest heat flow. It is caused by solar heat being absorbed at the exterior surface and by the temperature difference between the outdoor and indoor air.
Both heat sources are highly variable thruout any one day and, therefore, result in unsteady state heat flow thru the exterior construction. This unsteady state flow is difficult to evaluate for each individual situation; however, it can be handled best by means of an equivalent temperature difference across the structure.
The equivalent temperature difference is that temperature difference which results in the total heat flow thru the structure as caused by the variable solar radiation and outdoor temperature. The equivalent temperature difference across the structure must take into account the different types of construction and exposures, time of day, location of the building latitude , and design conditions. The heat flow thru the structure may then be calculated, using the steady state heat flow equation with the equivalent temperature difference.
A rise in outdoor temperature reduces the amount of absorbed heat going to the outdoors and more flows thru the wall. This same process occurs with any type of wall construction to a greater or lesser degree, depending on the resistance to heat flow thru the wall and the thermal capacity of the wall.
These diagrams do not account for possible changes in solar intensity or outdoor temperature. This progression of heat gain to the interior may occur over the full hour period, and may result in a heat gain to the space during the night. If the equipment is operated less than 24 hours, i. Therefore, the heat gain estimate sun and transmission thru the roof and outdoor walls , even with equipment operating less than 24 hours, may be evaluated by the use of the equivalent temperature data presented in Tables 19 and Basis of Tables 19 and 20 - Equivalent Temperature Difference for Sunlit and Shaded Walls and Roofs Table 19 and 20 are analogue computer calculations using Schmidts method based on the following conditions: Solar heat in July at 40 North latitude.
Outdoor daily range of dry-bulb temperatures, 20 deg F. Maximum outdoor temperature of 95 F db and a design indoor temperature of 80 F db, i.
Dark color walls and roofs with absorptivity of 0. For light color, absorptivity is 0. Sun time. The specific heat of most construction materials is approximately 0.
Use of Tables 19 and 20 - Equivalent Temperature Difference for Sunlit and Shaded Wall and Roofs The equivalent temperature differences in Tables 19 and 20 are multiplied by the transmission coefficients listed in Tables 21 thru 33 to determine the heat gain thru walls and roofs per sq ft of area during the summer.
The total weight per sq ft of walls and roofs is obtained by adding the weights per sq ft of each component of a given structure. These weights and shown in italics and parentheses in Tables 21 thru A flat roof exposed to the sun, with built-up roofing,1 1 2 in. Equivalent temperature difference at 4 p. The corrections to be applied to the equivalent temperature difference for combinations of these two variables are listed in the notes following Tables 19 and Equivalent temperature difference under changed conditions Solution: Occasionally the heat gain thru a wall or roof must be known for months and latitudes other than those listed in Note 3 following Table This equivalent temperature difference is determined from the equation in Note 3.
This equation adjusts the equivalent temperature difference for solar radiation only. Additional correction may have to be made for differences between outdoor and indoor design temperatures other than 15 deg F. Refer to Tables 19 and 20, pages 62 and 63, and to the correction Table 20A. Corrections for these differences must be made first; then the corrected equivalent temperature differences for both sun and shade must be applied in corrections for latitude.
Equivalent temperature difference in November at 12 noon. Load Estimating Chapter 5. The correction for design temperature difference is as follows: Equivalent temperature differences for 12 in. For other conditions, refer to corrections on page Weight per sq ft values for common types of construction are listed in Tables 21 thru Weight per sq ft values for common types of construction are listed in Tables 27 or Add the corrections listed in Table 20A, where the outdoor design temperature Table 1, page 10 minus the room or indoor design temperature table 4, page 20 is different from 15 deg F db, or the daily range is different from the 20 deg F db on which Table 19 and 20 are based.
This correction is to be applied to both equivalent temperature difference values, exposed to sun and shaded walls or roof. Shaded walls For shaded walls on any exposure, use the values of equivalent temperature difference listed for north shade , corrected if necessary as shown in Correction 1.
Latitudes other than 40 North and for other months with different solar intensities. Tables 19 and 20 values are approximately correct for the east or west wall in any latitude during the hottest weather. In lower latitudes when the maximum solar altitude is 80 to 90 the maximum occurs at noon , the temperature difference for either south or north wall is approximately the same as a north or shade wall.
See Table 18 for solar altitude angles. The temperature differential te for any wall facing or roof and for any latitude for any month is approximated as follows: Example 3 illustrates the procedure.
Light or medium color wall or roof Light color wall or roof: Other latitude, other month, light or medium color walls or roof. The combined formulae are: For South latitudes, use the following exposure values from Table The rate times the temperature difference is the heat flow thru the structure. The reciprocal of the U value for any wall is the total resistance of this wall to heat flow to the of heat.
The total resistance of any wall to heat flow is the summation of the resistance in each component of the structure and the resistances of the outdoor and inside surface films. The transmission coefficients listed in Tables 21 thru 33 have been calculated for the most common types of construction. The resistance of the outdoor surface film coefficient for summer and winter conditions and the inside surface film is listed in Table The difference between summer and winter transmission coefficients for a typical wall is negligible.
For example, with a transmission coefficient of 0. Example 4 Transmission Coefficients Given: Masonry partition made of 8 in. Transmission coefficient Solution: Frequently, fibrous insulation or reflective insulation is included in the exterior building structure.
The transmission coefficient for the typical constructions listed in Table 21 thru 30, with insulation, may be determined from Table 31, page Masonry wall consisting of 4 in. Transmission coefficient. Refer to Tables 22 and Difference between summer and winter transmission becomes greater with larger U values and less with smaller U values. Use of Tables 21 thru 33 - Transmission Coefficients U for Walls, Roofs, Partitions, Ceilings, floors, Doors, and Windows The transmission coefficients may be used for calculating the heat flow for both summer and winter conditions for the average application.
For types of construction not listed in Tables 21 thru 33, calculate the U value as follows: Determine the resistance of each component of a given structure and also the inside and outdoor air surface films from Table One column lists the thermal resistance per inch thickness, based on conductivity, while the other column lists the thermal resistance for a given thickness or construction, based on conductance. Transmission coefficient in summer.
Refer to Table Resistance Construction R 1. Outdoor air surface 7 1 2 mph wind 0. Stone facing, 2 in. Hollow clay tile, 8 1. Sand aggregate plaster, 2 in.
Inside air surface still air 0. Redwood, Hemlock, or Fir 2. Winter Horiz. In cases where the insulation froms a boundary highjly refiective of on air space, refer to Table 31, page The loss through the floor is normally small and relatively constant year round because the ground temperature under the floor varies only a little throughout the year. The ground is a very good heat sink and can absorb or lose a large amount of heat without an appreciable change in temperature at about the 8 ft level.
Above the 8 ft level, the ground temperature varies with the outdoor temperature, with the greatest variation at the surface and a decreasing variation down to the 8 ft depth.
The heat loss thru a basement wall may be appreciable and it is difficult to calculate because the ground temperature varies with depth. Tables 35 thru 37 have been empirically calculated to simplify the evaluation of heat loss thru basement walls and floors.
The heat loss thru a slab floor is large around the perimeter and small in the center. This is because the ground temperature around the perimeter varies with the outdoor temperature, whereas the ground temperature in the middle remains relatively constant, as with basement floors.
The perimeter factors listed in Table 36 were developed by calculating the heat transmitted for each foot of wall to an 8 ft depth. The ground was assumed to decrease the transmission coefficient, thus adding resistance between the wall and the outdoor air. The transmission coefficients were then added to arrive at the perimeter factors.
Use of Tables 35 thru 37 - Heat Loss thru Masonry Floors and Walls in Ground The transmission coefficients listed in Table 35 may be used for any thickness of uninsulated masonry floors where there is good contact between the floor and the ground. The perimeter factors listed in Table 36 are used for estimating heat loss thru basement walls and the outside strip of basement floors.
This factor can be used only when the space is heated continuously. If there is only occasional heating, calculate the heat loss using the wall or floor transmission coefficients as listed in Tables 21 thru 33 and the temperature difference between the basement and outdoor air or ground as listed in Table The heat loss in a basement is determined by adding the heat transferred thru the floor, the walls and the outside strip of the floor and the portion of the wall above the ground level.
Example 7- Heat Loss in a Basement Given: Basement Basement temp F db, heated continuously F db Outdoor temp-o Grade line-6 ft above basemen floor Walls and floors in. Heat loss from basement Solution: Heat loss thru walls and outside strip of floor below ground.
The factors in Tables 35 and 36 may be used for any thickness of uninsulated masonry wall or floor, but there must be a good contact no air space which may connect to the outdoors between the ground and the floor or wall. Where the ground is dry and sandy, or where there is cinder fill along wall or where the wall has a low heat transmission coefficient, the perimeter factor may be reduced slightly.
These coefficients may be useful in applications such as cold water or brine storage systems and ice skating rinks. It is also based on a low rate of circulation on the outside of the pipe and 10 F to 15 F temperature difference between water or brine and refrigerant. High rates of circulation will increase the heat transfer rate. For special problems, consult heat transfer reference books.
Water vapor flows thru building structures, resulting in a latent load whenever a vapor pressure difference exists across a structure. The latent load from this source is usually insignificant in comfort applications and need be considered only in low or high dewpoint applications. Water vapor flows from high to lower vapor pressure at a rate determined by the permeability of the structure. This process is quite similar to heat flow, except that there is transfer of mass with water vapor flow.
As heat flow can be reduced by adding insulation, vapor flow can be reduced by vapor barriers. The vapor barrier may be paint aluminum or asphalt , aluminum foil or galvanized iron. It should always be placed on the side of a structure having the higher vapor pressure, to prevent the water vapor from flowing up to the barrier and condensing within the wall.
Basis of Table 40 - Water Vapor Transmission thru Various Materials The values for walls, floors, ceilings and partitions have been estimated from the source references listed in the bibliography. The resistance of a homogeneous material to water vapor transmission has been assumed to be directly proportional to the thickness, and it also has been assumed that there is no surface resistance to water vapor flow.
The values for permeability of miscellaneous materials are based on test results. Some of the values for walls, roofs, etc.
Use of Table 40 - Water Vapor Transmission thru Various Materials Table 40 is used to determine latent heat gain from water vapor transmission thru building structures in the high and low dewpoint applications where the air moisture content must be maintained.
Example 8 Water Vapor Transmission Given: The outdoor wall is 12 inch brick with no windows. The partitions are metal lath and plaster on both sides of studs. Floor and ceiling are 4 inch concrete. The latent heat gain from the water vapor transmission. Latent heat gain: Insulating board lath 4. Two coats of a good vapor seal paint on a smooth surface give a fair vapor barrier.
More surface treatment is required on a rough surface than on a smooth surface. Data indicates that either asphalt or aluminum paint are good for vapor seals. Aluminum Foil on Paper: This material should also be applied over a smooth surface and joints lapped and sealed with asphalt. The vapor barrier should always be placed on the side of the wall having the higher vapor pressure if condensation of moisture in wall is possible. The heat gain due to water vapor transmission through walls may be neglected for the normal air conditioning or refrigeration job.
This latent gain should be considered for air conditioning jobs where there is a great vapor pressure difference between the room and the outside, particularly when the dewpoint inside must be low. Note that moisture gain due to infiltration usually is of much greater magnitude than moisture transmission through building structures. Conversion Factors: To convert above table values to: Whenever there is a difference of temperature and pressure of water vapor across a structure, conditions may develop that lead to a condensation of moisture.
This condensation occurs at the point of saturation temperature and pressure. As water vapor flows thru the structure, its temperature decreases and, if at any point it reaches the dewpoint or saturation temperature, condensation begins.
As condensation occurs, the vapor pressure decreases, thereby lowering the dewpoint or saturation temperature until it corresponds to the actual temperature. The rate at which condensation occurs is determined by the rate at which heat is removed from the point of condensation.
As the vapor continues to condense, latent heat of condensation is released, causing the dry-bulb temperature of the material to rise. To illustrate this, assume a frame wall with wood sheathing and shingles on the outside, plasterboard on the inside and fibrous insulation between the two.
The temperature and vapor pressure gradient decreases approximately as shown by the solid and dashed lines until condensation begins saturation point. At this point, the latent heat of condensation decreases the rate of temperature drop thru the insulation. This is approximately indicated by the dotted line. Another cause of concealed condensation may be evaporation of water from the ground or damp locations.
Concealed condensation may cause wood, iron and brickwork to deteriorate and insulation to lose its insulating value.
These effects may be corrected by the following methods: Provide vapor barriers on the high vapor pressure side. In winter, ventilate the building to reduce the vapor pressure within.
No great volume of air change is necessary, and normal infiltration alone is frequently all that is required. In winter, ventilate the structure cavities to remove vapor that has entered.
Outdoor air thru vents shielded from entrance of rain and insects may be used. Condensation may also form on the surface of a building structure. Visible condensation occurs when the surface of any material is colder than the dewpoint temperature of the surrounding air. In winter, the condensation may collect on cold closet walls and attic roofs and is commonly observed as frost on window panes. Point A represents the room conditions; point B, the dewpoint temperature of the thin film of water vapor adjacent to the window surface; and point C, the point at which frost or ice appears on the window.
Once the temperature drops below the dewpoint, the vapor pressure at the window surface is also reduced, thereby establishing a gradient of vapor pressure from the room air to the window surface. This gradient operates, in conjunction with the convective action within Tive action within the room, to move water vapor continuously to the window surface to be condensed, as long as the concentration of the water vapor is maintained in a space.
Visible condensation is objectionable as it causes staining of surfaces, dripping on machinery and furnishings, and damage to materials in process of manufacture. Condensation of this type may be corrected by the following methods: Increase the thermal resistance of walls, roofs and floors by adding insulation with vapor barriers to prevent condensation within the structures. Increase the thermal resistance of glass by installing two or three panes with air space s between.
In extreme cases, controlled heat, electric or other, may be applied between the glass of double glazed windows. Maintain a room dewpoint lower than the lowest expected surface temperature in the room.
Decrease surface resistance by increasing the velocity of air passing over the surface. Decreasing the surface resistance increases the window surface temperature and brings it closer to the room dry-bulb temperature. Basis of Chart 2 - Maximum Room RH; No Wall, Roof or Glass Condensation Chart 2 has been calculated from the equation used to determine the maximum room dewpoint temperature that can exist with condensation.
Chart 2 is based upon a room dry-bulb temperature of 70 F db and an inside film conductance of 1. Use of Chart 2 - Maximum Room RH; No Wall, Roof or Glass Condensation Chart 2 gives a rapid means of determining the maximum room relative humidity which can be maintained and yet avoid condensation with a 70 F db room.
Example 9-Moisture Condensation Given: Maximum room rh without wall condensation. Values other than those listed may be interpolated. Example Moisture Condensation Given: Same as Example 9, except room temp is 75 F db Find: Maximum room rh without wall condensation Solution: These outdoor air quantities normally have a different heat content than the air within the conditioned space and, therefore, impose a load on the air conditioning equipment.
In the case of infiltration, the load manifests itself directly within the conditioned space. The ventilation air, taken thru the conditioning apparatus, imposes a load both on the space thru apparatus bypass effect, and directly on the conditioning equipment. This opposite direction flow balances at some neutral point near the mid-height of the building.
Air flow thru the building openings increases proportionately between the neutral point and the top and the neutral point and bottom of the building. The infiltration from stack effect is greatly influenced by the height of the building and the presence of open stairways and elevators. The combined infiltration from wind velocity and stack effect is proportional to the square root of the sum of the heads acting on it. The increased air infiltration flow caused by stack effect is evaluated by converting the stack effect force to an equivalent wind velocity, and then calculating the flow from the wind velocity data in the tables.
In building over ft tall, the equivalent wind velocity may be calculated from the following formula, assuming a temperature difference of 70 F db winter and a neutral point at the mid-height of the building: The total crackage is considered when calculating infiltration from stack effect.
Stack effect is not normally a significant factor because the density difference is slight, 0. This small stack effect in tall buildings over ft causes air to flow in the top and out the bottom. Therefore, the air infiltrating in the top of the building, because of the wind pressure, tends to flow down thru the building and out the doors on the street level, thereby offsetting some of the infiltration thru them. Infiltration of air and particularly moisture into a conditioned space is frequently a source of sizable heat gain or loss.
The quantity of infiltration air varies according to tightness of doors and windows, porosity of the building shell, height of the building, stairwells, elevators, direction and velocity of wind, and the amount of ventilation and exhaust air.
Many of these cannot be accurately evaluated and must be based on the judgment of the estimator. Generally, infiltration may be caused by wind velocity, or stack effort, or both: Wind Velocity-The wind velocity builds up a pressure on the windward side of the building and a slight vacuum on the leeward side. The outdoor pressure build-up causes air to infiltrate thru crevices in the construction and cracks around the windows and doors.
This, in turn, causes a slight build-up of pressure inside the building, resulting in an equal amount of exfiltration on the leeward side. Difference in Density or Stack Effect The variations in temperatures and humidities produce differences in density of air between inside and outside of the building. In tall buildings this density difference causes summer and winter infiltration and exfiltration as follows: Summer Infiltration at the top and exfiltration at the bottom.
Winter Infiltration at the bottom and exfiltration at the top. Load Estimating Chapter 6. Infiltration And Ventilation In low buildings, air infiltrates thru open doors on the windward side unless sufficient outdoor air is introduced thru the air conditioning equipment to offset it; refer to Offsetting Infiltration with Outdoor Air.
With doors on opposite walls, the infiltration can be considerable if the two are open at the same time. This data is derived from Table 44 which lists infiltration thru cracks around windows and doors as established by ASHAE tests. Table 41d shows values to be used for doors on opposite walls for various percentages of time that each door is open.
The data in Table 41e is based on actual tests of typical applications. Use of Table 41 - Infiltration thru Windows and Doors, Summer The data in Table 41 is used to determine the infiltration thru windows and doors on the windward side with the wind blowing directly at them. When the wind direction is oblique to the windows or doors, multiply the values in Tables 41a, b, c, d, by 0.
For specific locations, adjust the values in Table 41 to the design wind velocity; refer to Table 1, page During the summer, infiltration is calculated for the windward side s only, because stack effect is small and, therefore, causes the infiltration air to flow in a downward direction in tall buildings over ft. Some of the air infiltrating thru the windows will exfiltrate thru the windows on the leeward side s , while the remaining infiltration air flows out the doors, thus offsetting some of the infiltration thru the doors.
To determine the net infiltration thru the doors, determine the infiltration thru the windows on the windward side, multiply this by. For low buildings the door infiltration on the windward side should be included in the estimate. Revolving Doors-Normal Operation. When the wind direction is oblique to the window or door, multiply the above values by 0. Based on a wind velocity of 7. For design wind velocities different from the base, multiply the above values by the ratio of velocities. Includes frame leakage where applicable.
When door usage is heavy, the vestibule is of little value for reducing infiltration. A story building in New York City oriented true north.
Building is ft long and ft wide with a floor-to-floor height of 12 ft. There are ten 7 ft 3 ft swinging glass doors on the street level facing south. Infiltration into the building thru doors and windows, disregarding outside air thru the equipment and the exhaust air quantity. The prevailing wind in New York City during the summer is south, 13 mph Table 1, page Therefore, there is no infiltration thru the doors on the street level on design days, only exfiltration. The outdoor air so introduced must develop a pressure equal to the wind velocity to offset infiltration.
This pressure causes exfiltration thru the leeward walls at a rate equal to wind velocity. Therefore, in a four sided building with equal crack areas on each side and the wind blowing against one side, the amount of outdoor air introduced thru the apparatus must be a little more than three times the amount that infiltrates. Where the wind is blowing against two sides, the outdoor air must be a little more than equal to that which infiltrates. Offsetting swinging door infiltration is not quite as difficult because air takes the path of least resistance, normally an open door.
Most of the outdoor air introduced thru the apparatus flows out the door when it is opened. Also, in tall building the window infiltration tends to flow out the door.
The infiltration thru revolving doors is caused by displacement of the air in the door quadrants, is almost independent of wind velocity and, therefore, cannot be offset by outdoor air. Basis of Table 42 - Offsetting Swinging Door Infiltration with Outdoor Air, Summer Some of the outdoor air introduced thru the apparatus exfiltrates thru the cracks around the windows and in the construction on the leeward side. The outdoor air values have been increased by this amount for typical application as a result of experience.
Use of Table 42 - Offsetting Swinging Door Infiltration with Outdoor Air, Summer Table 42 is used to determine the amount of outdoor air thru air conditioning apparatus required to offset infiltration thru swinging doors.
A restaurant with cfm outdoor air being introduced thru the air conditioning apparatus. Exhaust fans in the kitchen remove cfm. Two 7 ft 3 ft glass swinging doors face the prevailing wind direction. At peak load conditions, there are people in the restaurant.C wiLh 2 '0pfflii;11CS i. Chapter 3, Heat Storage, Diversity and Stratification, contains the data and methods for estimating the actual cooling load from the heat sources referred to in the following text.
This raises the temperature of the first slice above that of the outdoor air and the second slice, causing heat to flow to the outdoor air and also to the second slice, Fig.
The upper curve represents the instantaneous heat gain and the lower curve the actual cooling load for that day with a constant temperature maintained within the space during the operating period of the equipment. Basis of Table 15 - Solar heat Gain thru Ordinary Glass Table 15 provides data for 0, 10, 20, 30, 40, and 50 latitudes, for each month of the year and for each hour of the day. The capacity of these fans has been arbitrarily taken at fpm minimum and fpm maximum outlet velocity.
The practice of drastically lowering the temperature to 50 F db or 55 F db when the building is unoccupied precludes the selection of equipment based on such capacity reduction. Aiii' I.. The data in Table 41e is based on actual tests of typical applications. T" 6 contains the estimating data.