1、STD.ASHRAE SRCH IJHVAC +Z-NGL 5778 D 0759b50 0535277 110 STD-ASHRAE SRCH IJHVAC Li-2-ENGL 1998 W 0759b50 0535300 7b2 = International Journal of Heating, Ventilating, Air-Conditioning and Refrigerating Research Editor Raymond Cohen, Ph.D., P.E., Professor of Mechanical Engineering and Henick Professo
2、r of Engineering, Purdue University, U.S.A. Associate Editors Arthur E. Bergles, Ph.D., P.E., John A. Clark and Edward T. Crossan Professor of Engineering Emeritus, Department of Mechanical Engineering, Aeronautical Engineering and Mechanics, Rensselaer Polytechnic Institute, U.S.A. Arthur L. Dexter
3、, D.Phil., C.Eng., Reader in Engineering Science, Department of Engineering Science, University of Oxford, United Kingdom David A. Didion, D.Eng., P.E., Leader, Thermal Machinery Group, Building and Fire Research Laboratory, National Institute of Standards and Technology, U.S.A. Ralph Goldman, Ph.D.
4、, Senior Consultant, Arthur D. Little, Inc., U.S.A. Hugo Hens, Dr.Ir., Professor, Department of Civil Engineering, Laboratory of Building Physics, Katholieke Universiteit, Belgium Ken-Ich Kimura, Dr. Eng., Professor, Department of Architecture, Waseda University and President, Society of Heating, Ai
5、r-conditioning and Sanitary Engineers of Japan, Japan Universitt Hannover, Germany Universit de Lige, Belgium University of Wisconsin-Madison, U.S.A. University of California, Santa Barbara, U.S.A. Horst Kruse, Dr.-lng., Professor, Institut fr Kltetechnik und Angewandte Wrmetechnik, Jean J. Lebrun,
6、Ph.D., Professor, Laboratoire de Thermodynamique, John W. Mitchell, Ph.D., P.E., Professor, Mechanical Engineering, Dale E. Seborg, Ph.D., Professor, Chemical Engineering, Policy Committee William J. Coad, chair Hans O. Spauschus Fritz W. Steimle Frank M. Coda W. Stephen Comstock Raymond Cohen Edito
7、rial Assistant Jenny Otlet-Jakovljevic QI998 by the American Society of Heating, Refngerating and Air-Con- ditioning Engineers. Inc 1791 Tullie Circle, Atlanta. Georgia 30329. All rights reserved. Periodicals postage paid at Atlanta. Georgia. and additional mailing offices. HVAC nor may any pari of
8、this book be reproduced, stored in a retrieval system. or Publisher Frank M. Coda Publishing Director W. Stephen Comstock ASHRAE Editorial and Publishing Services Staff Robert A. Parsons, Handbook Editor Scott A. Zeh, Publishing Services Manager Nancy F. Thysell, Typographer msmitted in any form or
9、by any means-zlectmnic, photocopying. recording. or other-without permission in writing from ASHRAE. Abstrac1 X + (2n + 1)Yl2 M = 1.0 for 2-R The additive flue function Fis given by 3(Xc-X) R F = nY(Zf- l)?( 1 - Wf+ 1) 7 where 2(1 -R-Y) X, = R+ - 2Y(zf- I)“ n+l 123 The flue factor Fin Equation (9) i
10、s always additive because the flue outlet is the highest leak- age site and will always act to increase the ventilation flows. With very strong flue exfiltration, even the ceiling can become an infiltration site, through which attic air is drawn into the building. The variable X, is the critical val
11、ue of the ceiling-fioor leakage difference X at which the neutral level (zero indoor to outdoor pressure difference) is located at the ceiling in the exact numerical solution. For X X, the neutral level will be above the ceiling, and air will flow in through the ceiling. For X Tout, and will be reve
12、rsed if Tour Tin.) The role of the flue in reducing ceiling exfiltration is evident from the contribution of the Y factor in Equation (1 3). The stack factorf, from Equation (9) is shown in Figure 1 for typical values of n = 0.67, Zr= 1.5, and Y = 0.2, and for no flue, Y = O. Figure 1 shows that tre
13、ating the flue as a separate leakage site with a stack height above the ceiling has a significant effect on the stack factorf,. In addi- tion, Figure 1 shows the reduction in they were numbered four and five at the test facility. An important aspect of the test facility is that the houses were situa
14、ted in rural terrain. Because the houses were in an east-west row they were unsheltered for winds from the North and South and pro- vided strong shelter for each other for east and west winds. Envelope leakage characteristics were measured in the two houses using a fan pressurization test over the r
15、ange from 1 Pa to 75 Pa, from which C, n, and the 4 Pa leakage area A4 were deter- mined (see Table 2). To remove the effect of building size on the predictions the ventilation rates were converted from m3/s to air changes per hour (ACH) by dividing by the building vol- ume (approximately 220 m3 for
16、 the test houses in this study). The leakage distribution was estimated by visual inspection at the test facility. For House #4 with the flue blocked it was estimated that R = 0.5, X = O, Y = O. For House #4 with a 75 mm diameter orifice in a 150 mm diameter flue it was estimated that R = 0.3, X = O
17、, Y = 0.4. For 130 HVAC 0.00 .- CI - .- .ad c VOLUME 4, NUMBER 2, APRIL 1998 131 .25n,rs,maa I, -8 Io ,u ,Ia I III 8 sus 1-s- 8 8 tqxInu I 3 - - “ Figure 3. Comparison of ventilation models with measured data for unshielded windspeed dependence (north and south winds) in House #5 (with open, 150 mm
18、diameter flue, AT c 10 K, and U 1.5 mis for 279 hours) I 132 HVAC: 0.00 8 11 I I r Q 118 8 8 I 9 9, 8 I, 9 -1 r 8 *i 18, 8 I 8 8 WI I 10 1 I :a 8 e D- - 0 D D o AIM-2 lP “l“ii“l“l“ .30 = .20 a 0.00“1.1,1.I 12 3 4 5 I s 6 I. 7 I I .I“I“.i 8 9 10 U, Wind Speed m/s Figure 6. Comparison of ventilation m
19、odels with measured data for shielded windspeed dependence (east and west winds) in House #5 (with open 150 mm diameter flue, AT 1.5 m/s for 461 hours) sets introduced large errors into the model predictions of Shaw and Warren and Webb. In most cases the LBL model had the greatest scatter. This was
20、because its assumption of orifice flow for the building envelope produces an incorrect variation in ventilation rate with wind speed and temperature difference. Sensitivity to Leakage Distribution One of the most difficult input parameters to estimate is the distribution of leakage between the floor
21、, walls and ceiling. To estimate the magnitude of variation likely to occur in ventilation rates predicted using different leakage distributions, an informal survey of the staff working at Alberta Home Heating Research Facility was conducted. The survey resulted in eight different estimates of leaka
22、ge distribution for House #4. STD.ASHRAE SRCH IJHVAC Li-2-ENGL 1798 0759b.50 0535337 Tbb 133 VOLUME 4, NUMBER 2, APRIL 1998 6 .20 0 a, e .I5 c O CI .- - ia .lo .- Y C .O5 Shaw AIM-2 LBL ME Wamtn 8 Wbb 0.00 I I I I I I 1 1 O 5 10 15 20 25 30 35 AT, Indoor-outdoor temperature difference “CI Figure 7.
23、Comparison of ventilation models to measured data for temperature difference dependence in House #4 (with open 75 mm diameter orifice in flue, AT 10 K, U To, and the neutral pressure plane lies below the ceiling. The same approach was used for other cases, but not given here, for brevity. The height
24、 of each leak was given in non-dirnensionalized form (Z). It was non-dimensionalized by dividing by the height of the ceil- ing above grade. At the neutral pressure plane: 2 = Z,. Ceiling leaks have outflow. Floor leaks have inflow. The fumaceAireplace flue(s) have outflow. The walls have inflow bel
25、ow the neutral level and outflow above it. Also, the flow generated by the pressure difference profile must be integrated over the wall due to the non-linearity of flow with pressure. For this integration, an element of the wall was determined by its fraction of the total wall height and is given by
26、: C,dZ dC, = 7 This fractional wall height was expressed in nondimensional height Assuming that the leaks are evenly distributed with height over the wall, then the incremental flow de, to be integrated becomes I i 36 HVAC n+l Equations (Al), (A2), (A3), (Ag) and (A9) can be written in terms of R, X
27、, and Y, and all the inflow terms grouped together to give Similarly for the outflows (1-R-Y) Qstackoui - CAP;?( 1 - 2,)“ + n+ 1 (1 -Zo)n+l + Y(Z,-Z,)“ (All) Setting the inflows and outflows equal gives a single equation, with a single unknown Z, 2(1 -R- Y) RIZo-(l-Zo)n+ + - (1 -Z0)“ + I - 2Y(z,-z0)
28、“ (A 12) n+l X= z0+(1-z,)“ Z, was found using a Newton-Raphson technique. The net infiltration rate was found by averaging the inflow and outflow together and substitut- ing Equation (A12) for X. After considerable algebraic manipulation, the stack factor was given by 1+nR-Y f, = z0+(1-z0)“ The neut
29、ral level determined from the solution to Equation (A12) was substituted in Equation (A13) to obtain a numerical value of the stack factor. STD-ASHRAE SRCH IJHVAC Li-Z-ENGL 1998 = 0759b50 0535323 997 = VOLUME 4, NUMBER 2. APRIL 1998 137 Wind Effect For wind effect, the pressure across each leak was
30、determined by the pressure coefficient on the exterior surface Cpi and the interior pressure coefficient Cp, that acts to balance the inflows and outflows. For leak i The wind induced flow at each leakage site was then determined by the flow coefficient for each site and the pressure difference calc
31、ulated using Equation (A14). Setting the inflow and outflow to be equal resulted in a single equation that is solved for the interior pressure coefficient. Each Cp was taken from measured wind tunnel data. The ceiling Cp and floor Cp were dis- cussed in the main text. The flue pressure coefficient o
32、f -0.5 was taken from measured data by Haysom and Swinton (1987) and was corrected for the increased wind speed at the flue top com- pared to the reference wind speed at eaves height. Using the exponentp from the boundary layer wind profile Cpflue = -0.59 0415) A value of p = 0.17 was used here. Ass
33、uming a slab on grade or basement house the flow for the walls and floors is given by Equation (A16). The procedure for a crawlspace is the same except that the floor level leaks were expressed separately. The flow for the ceiling was given by and the flow through the flue(s) was Cpin is then found
34、by grouping the inflows and outflows together (by looking at the sign of the pressure difference across each leak) and equating them. The resulting equation was then solved using a Newton-Raphson numerical technique. The resulting flows were then used to determine the wind factorf,. NOMENCLATURE A,
35、effective leakage area for 4.0 Pa pressure dif- ference, m2 m3/(s.Pan) at H C, leakage flow coefficient C of ceiling, A; area of wail i, m2 Cf leakage flow coefficient C of floor level B, leaks, rn3/(s.pan) CJUe leakage flow coefficient C of flue and fire- wind and stack effect pressure interaction
36、coefficient places, m3/(s.Pan) at H, C flow coefficient, m3/(s.pan) C, ieakage of iais,-m3/(S.an) STD-ASHRAE SRCH IJHVAC 4-2-ENGL 1990 0759b50 0535322 323 138 HVACBrR RESEARCH Cp wind pressure coefficient Qwullin inflow through wall, m3/s Cpcejlrng wind pressure coefficient for ceiling leaks Cpfl, w
37、ind pressure coefficient for fluefireplace Cp, wind pressure coefficient for leak i R* crawlspace wind factor parameter for R Cpin wind pressure coefficient for inside building sw total wind shelter factor Cpwall,i wind pressure coefficient for wall if, stack Qwallour outflow through wail, m3/s R co
38、mbined fraction of leakage in the floor top plus ceiling swo wind shelter factor for building Walls fw fwc F g H Hf Hmer J M n Pmer P Q factor wind factor wind factor for a house with a crawlspace flue function gravitational acceleration, m/s2 ceiling height of top story above floor (same as eaves h
39、eight), m height of flue outlet above floor, m height at which U, is measured, m wind factor parameter stack factor parameter pressure flow exponent power law exponent of wind speed profile at the meteorological station power law exponent of wind speed profile at the building site flow rate, m3/s Qc
40、eiling ceiling flow, m3/s Qflo, floor flow, m3/s Q, flue/fireplace flow, m3/s Q, stack effect flow, m3/s Qsruckrn stack effect inflow, m3/s QsrUckour stack effect outflow, m3/s Q,“ wind effect flow, m3/s Qwull wail flow, m3/s Qwual wail flow through wall i, m3/s Swfl, wind shelter factor for flues a
41、nd fireplaces Tjn indoor temperature, K Tou, outdoor temperature, K U wind speed at eaves height at the building site, ds Um, wind speed at the meteorological site, m/s X difference in leakage fraction between the floor and ceiling X, critical value of X for which neutrai level is at ceiling for sta
42、ck effect Xcri, critical value of X for which neutral level is at ceiling for wind effect Y shifted value of X for crawlspace wind factor crawlspace wind factor parameter for X flue leakage fraction crawlspace wind factor parameter for Y normalized height above floor normalized flue height normalize
43、d neutral pressure plane height area averaged height of terrain roughness elements building envelope pressure difference, Pa pressure across leak i, Pa stack effect reference pressure, Pa reference wind pressure, Pa indoor-outdoor temperature difference, K outdoor air density, kg/m3 REFERENCES Akins
44、, R.E., J.A. Peterka, and J.E. Cermak. 1979. Averaged Pressure Coefficients for Rectangular Build- ASHRAE. 1989. Air Flow Around Buildings. Chapter 14, ASHRAE Handbook-Fundamentals. Atlanta: ASTM. 1995. Determining Air Leakage by Fan Pressurization. ASTM Standard E 779-87. W. Consho- Beach, R.K. 197
45、9. Relative Airtightness of New Housing in the Ottawa Area. Building Research Note No. CGSB. 1986. Determination of Airtightness of Building Envelopes by the Fan Depressurization Method. CHBA. 1994. HOT2000 Technical Manual. Ottawa: Canadian Home Builders Association. Hamlin, T., and W. Pushka. 1994
46、. Predicted and Measured Air Change Rates in Houses with Predictions of Occupant IAQ Comfort. In Proc. 15th AIVC Conference, Buxton, UK, pp. 771-775. Haysom, J.C., and M.C. Swinton. 1987. The Influence of Termination Configuration on the Flow Perfor- mance of Flues. Canada Mortgage and Housing Corpo
47、ration Research Report. Ottawa: Mortgage and Housing Corporation. Irwin, J.S. 1979. A Theoretical Variation of the Wind Profile Power Law Exponent as a Function of Sur- face Roughness and Stability. Atmospheric Environment (13): 191-194. ings. Wind Engineering Vol. 1, In Proc. 5th Int. Wind Engineer
48、ing Conference. pp. 369-380. ASHRAE. hocken, PA: American Society for Testing and Materials. 149. Ottawa: National Research Council Canada. CGSB Standard 149.1 -M86. Ottawa: Canadian General Standards Board. STD-ASHRAE SRCH IJHVAC q-Z-ENGL 1798 0757b50 0535323 2bT VOLUME 4, NUMBER 2, APRIL 1998 139
49、Liddament, M.W. 1986. Air Infiltration Calculation Techniques-An Applications Guide. Bracknell, U.K: Air Infiltration and Ventilation Center. Palmiter, L., and T. Bond. 1994. Modeled and Measured Infiltration II-A Detailed Case Study of Three Homes. Electric Power Research Institute Repon TR 1025 11. Palo Alto, CA: Electric Power Research Institute. Palmiter, L., and T. Bond. 1991. Interaction of Mechanical Systems and Natural Infiltration. In Proc. 12th AIVC Conference, Ottawa
