Abstract
This paper aims to clarify the effects of extreme weather conditions on the space thermal comfort and energy consumption, which depend on the thermal characteristics of buildings and HVAC systems. Various types of extreme weather days that occur in Tokyo were picked from Expanded AMeDAS weather data for the period 1981 to 1995. Computer simulations were performed for office spaces, using 15-year Tokyo weather data to obtain the hourly changes in the PMV and the load on each of the components in a HVACsystem. The type of extreme weather day that created severe conditions from the standpoint of thermal comfort and equipment load was clarified. Keywords: extreme weather day; thermal comfort; equipment load; expanded AMeDAS weather data; office space 1. Introduction from weather data for the period from 1981 to 1995 For the economical and correct sizing of heating, ven- based upon the daily weather indices. The following three tilating and air-conditioning (HVAC) equipment, design- types of winter extreme weather days selected occurred ers popularly use design weather data that allows for between December and March. the risk occurrence of the more extreme weather con- Type A: The day when the daily minimum of the out- ditions. In this paper, we attempt to define the loads that door air temperature was at the minimum for are imposed on the HVAC equipment in order to keep the 15-year period. the space or room temperature at the set point, and how Type B: The day when the daily average of the outdoor the space thermal environment deteriorates on days air temperature was at the minimum for the 15- where extreme weather is experienced. Various types of year period. extreme weather were selected from actual events in Type C: The day when the daily average of the outdoor Tokyo occurring during the years from 1981 to 1995, air enthalpy was at the minimum for the 15- using Expanded AMeDAS weather data. Computer simu- year period. lations were performed to obtain the space thermal en- The Four types of the summer extreme weather days vironment and the equipment loads required to maintain selected occurred during June and September. set point space temperature throughout 15 years. The Type A: The day when the daily maximum of the out- effect of the extreme weather on the space thermal com- door air temperature was at the maximum for fort and the equipment load may be dependent upon the the 15-year period. kind of HVAC equipment, the space zoning, and the build- Type B: The day when the daily average of the outdoor ing thermal characteristics such as window orientation. air temperature was at the maximum for the The effect of extreme weather on the space thermal 15-year period. comfort and the equipment load was analyzed with re- Type C: The day when the daily average of the outdoor spects to these points. The results obtained are valuable air enthalpy was at the maximum for the 15- for the proposal of better design weather data to ensure year period. adequate and economical sizing in future HVAC designs. Type D: The day when the daily total of solar radiation on a horizontal or vertical surface was at the 2. Selection of the Extreme Weather Days maximum for the 15-year period. Various types of extreme weather days were selected Table 1. shows the dates and weather characteristics of the selected days. Each of the extreme weather days selected on the basis of one of the indices of outdoor air Contact Author: Kimiko Kohri, Associate Prof., Dept. of temperature or enthalpy, can also be regarded as a con- Energy and Environmental Science, Graduate School of Eng., siderably extreme weather day based upon the other in- Utsunomiya Univ., 7-1-2 Yoto, Utsunomiya, 321-8585 Japan dices of outdoor air temperature or enthalpy. The day Tel: +81-28 -689-6189 Fax: +81-28-689-6194 that occurred before the selected day also tends to show e-mail:kohri@cc.utsunomiya-u.ac.jp (Received May 8, 2002; accepted August 16, 2002) Journal of Asian Architecture and Building Engineering/November 2002/64 57 characteristics of considerably extreme weather. (OT) was used as a combined index of space air tem- perature and radiant environment, and predicted mean 3. Simulation Model vote (PMV) was used as an index of thermal sensation. The simulation model is based on typical office space OT and PMV were calculated with the assumption that as shown in Figure 1. The space is conditioned by a the individual is at the center of each perimeter and inte- single air-handling unit (AHU) that has temperature and rior zone. The simulation conditions are given in Table humidity sensors in the interior zone, and fan coil units 2. The operation of the HVAC system is as follows. (FCU) that have a temperature sensor in the perimeter 1) The equipment capacity is enough and the space air zone. The air temperature of the perimeter zone, the temperature is assumed not to rise or fall owing to its interior zone, and the ceiling space as well as 11 surface limitations. Although water spray in the AHU meets the temperatures were obtained from solving convective and space requirements for humidification, dehumidification radiative heat balance equations. Operative temperature by cooling coils in the AHU and the FCU are not con- Table 1. The Extreme Weather Days in Tokyo Selected from Weather Data during the Years from 1981 - 1995 T he ranking of T he values of weat her indices *1 T he rank ing of ot her t he weat h er index T y p e of ext reme weat her *1 Dat e weat her in dices on t he used for select io n SRs or t omin t omax t oave hoave select ed day *2 on t he previous SRw day *2 Wint er T y p e A: t omin was at t he minimum Feb. 27 '81 -3.6 4.9 0.8 4.0 s 17.6 t oave 7t h , hoav e4t h t om in 23rd T y p e B: t oave was at t he minimum Jan. 21 '84 -2.2 0.7 -0.6 6.4 s 1.4 t om in 8t h , hoav e 24t h t oav e 6t h T y p e C: hoave was at t he minimum Feb. 7 '84 -3.1 2.7 0.1 2.8 s 18.0 t om in 3rd, t oav e 2nd hoave 10t h Summer T y p e A: t omax was at t he maximum Aug. 3 '94 27.8 37.9 32.3 74.9 s 7.6 t oave 2nd t om ax 5t h T y p e B: t oave was at t he maximum Aug. 4 '94 29.5 36.2 32.4 76.8 s 7.9 t om ax 5t h t oav e 11t h T y p e C: hoave was at t he maximum Aug. 7 '94 28.1 34.5 30.7 81.5 s 7.6 t oave 8t h ,t om ax 30t h hoave 26t h T y p e D: SRs was at t he maximum Sep . 26 '89 20.9 27.3 23.5 47.6 s 13.7 SRs 5t h T y p e D: SRw was at t he maximum Jun. 24 '87 19.4 27.9 23.7 50.8 w 13.4 SRw 14t h *1 t omin, t oave and t omax: daily minimum, daily average and daily maximum of out door air t emp . (deg C), hoave: daily average of out door air ent halp y (J/g), SRs and SRw: solar radiat ion on a sout h-facing surface and on a west -facing surface (M J/m2) *2 T he ranking of t he weat her indices among 1830 cooling day s or 1818 heat ing day s during t he y ears from 1981 t o 1995. T he ranking wit hin 50t h is writ t en in t he t able. AHU SP HC CC OA Peri meter Interi or zone z one EA FCU SP :Water spray HC:Heating coil 5m 5m CC:Cool ing c oi l Fig.1. An Office Space on a Typical Floor Table 2. The Conditions of the Building and the HVAC System for Simulations Building Structure: Curtain wall, Glazing: Clear s ingle glas s Blind operation: Clos ing blind is determined by the s unlit floor depth and the intens ity of trans mitted s olar radiation Occupancy: 0.2 pers on/m2, Lighting and equipment: 30W/m2 HVAC Set point s pace air temperature and humidity: 25deg C for cooling and 23deg C RH50% for heating s ys tem Heating and cooling hours : 8:00 - 18:00 (warm-up or pull-down 8:00 - 9:00) Heating s eas on: December to March, Cooling s eas on: June to September Fres h air rate: 1.1 lit/m2s ec, s upply airflow rate: AHU 5.0 lit/m2s ec, FCU 43 lit/ms ec Human Clothing and metablis m: o.6clo and 1.1 Met in cooling s eas on and 0.9 clo and 1.2 Met in heating s eas on, Air velocity: 0.2m/s ec 58 JAABE vol.1 no.2 November 2002 Kimiko Kohri Fig.2. The Changes in the Space Environment and the Equipment Load during the Winter Extreme Weather Days (in a south facing space) trolled and the dehumidification rate depends on the sen- assumed to be constant and the space air temperature is sible cooling rate. also assumed to reach set point at 0900. 2) The HVAC system operates every day during the cool- ing season from June to September and during the heat- 4. The Space Thermal Environment and the Equip- ing season from December to March. The AHU can ment Load during the Extreme Weather Days in a meet the interior zone demands of heating and cooling South-facing Office Space between December and March, but only cooling between 4.1 Changes of Space Temperature, Humidity and June and September. Thermal Loads 3) During the warming-up or pulling-down hours (from The simulation was performed for a south-facing of- 0800 to 0900), each value of AHU load and FCU load is fice space, using 15-year Tokyo weather data. Figure 2 JAABE vol.1 no.2 November 2002 Kimiko Kohri 59 illustrates the hourly changes in the space thermal envi- rior and perimeter zones is low during the space heating ronment and the equipment load during the winter ex- hours on that date. treme weather days of type A and B. To give a compari- Figure 3 illustrates the results of the summer extreme son for the average weather day, the average values of weather days of type A, C and D. On the extreme weather the weather, the thermal environment, and the thermal day of type A, the outdoor air temperature almost reached load at each hour in February for 15 years are also in- 38 C and the OT became higher than space air tempera- cluded. During the extreme weather days of type A, the ture by approximately 1.5K in the interior zone, and by space air temperatures declined considerably till approxi- approximately 2.5K in the perimeter zone. On the extreme mately 0600, and a large heating rate was required by weather day of type C, AHU loads became larger due to the AHU to warm-up. Alternatively, a relatively high the increase in the latent load of humid fresh air. On the amount of solar radiation meant that the perimeter zone extreme weather day of type D, FCU loads became did not require heating until 1700. During the extreme larger in order to remove the large amounts of solar heat weather day of type B, the rate of the thermal load on gained. However, the OT did not become higher as found the AHU and the FCU is large, and OT in both the inte- in the case of other extreme weather days. Fig.3. The Changes in the Space Environment and the Equipment Load during the Summer Extreme Weather Days (in a south facing space) 60 JAABE vol.1 no.2 November 2002 Kimiko Kohri 4.2 Evaluation by Ranking the PMV and Equipment environment at 1400 in each of the interior and perim- Load eter zones is the highest of four days. However, the Using the hourly PMV and the hourly equipment load PMV decreases after 1500 due to the sudden decrease calculated for 15 years, the ranking of the PMV and the of solar radiation. On the extreme weather day of type equipment load was obtained to quantify how much the B, the hours during which the ranking percentage of the space thermal environment deteriorates, and how much warm environment is within 1% are considerably longer heating or cooling is required to the HVAC equipment on when compared with the other three days. The extreme the extreme weather days in comparison with the nor- weather days of type A and B can be regarded as the mal days. For example, Figure 4 shows the ranking of most severe conditions for thermal comfort during the the warm space environment during cooling hours for cooling season. The ranking of the cooling AHU load 15 years using the PMV as an index. The ranking among becomes higher on the extreme weather day of type C. 18300 cooling hours is taken as the variable of the X- Although the ranking of the cooling FCU load becomes axis in the left-hand figure. In the right-hand figure, the high on the extreme weather day of type D, the ranking ranking is converted to the percentage of the total num- percentage does not fall within 1%. The FCU load be- ber of cooling hours and is expressed on a logarithmic comes much larger on those days with a high level of scale. This percentage means the probability of occur- air humidity, as well as intense solar radiation on the rence of the warmer space environment than that cor- window surface. On such days the FCU removes not responding to this percentage. The first ranking of the only sensible heat but also latent heat from the condi- PMV can be regarded as the warmest and the worst tioned space. space environment during the cooling hours for 15 yeas and its probability of occurrence is 0.005%. 5. The Space Thermal Environment and the Equip- The hourly changes in the PMV and the equipment ment Load during the Extreme Weather Days in a load, as well as their ranking during the winter extreme North or West-facing Office Space weather days, are shown in Figure 5. PMV values dur- The effect of extreme weather on the space thermal ing the extreme weather day of type A are similar to environment and the equipment load depends largely those on the extreme weather day of type C. During the upon the buildings thermal characteristics. During the extreme weather day of type B, the PMV has a con- simulations, the effects of different window orientation stantly low value, and the PMV at 0900 in each of the on each case were analyzed. Figure 7 illustrates the PMV interior zone and perimeter zone, ranks second (0.01% and the equipment load, as well as their ranking in a as a percentage expression) as the coldest environment north-facing office space during the winter extreme during heating hours for 15 years. On any of these three weather days. The ranking of the cold environment and days, the AHU load at 0900 becomes considerably larger. the equipment load both become high during the ex- In particular, the AHU load at 0900 on the extreme treme weather day of type B. This trend is similarly evi- weather day of type B ranks first in magnitude during dent in the case of a south-facing office space. Figure 8 heating hours. The FCU load on the extreme weather shows the PMV and the equipment load, as well as their day of type B maintains a high value, and its ranking ranking in a west-facing office space during the sum- percentage is within 1% throughout the day. mer extreme weather days. On the extreme weather days Figure 6 demonstrates the hourly changes of the PMV of type A and C, the PMV ceases to increase at around and the equipment load, as well as their ranking during 1600, and its changes are similar to those in a south- the summer extreme weather days. On the extreme facing office. This is due the decrease in solar radiation weather day of type A, the ranking of the warm space after 1500. As a result, the extreme weather day of type Fig.4. The Ranking of the Warm Space Environment during Cooling Hours for 15 Years Using the PMV as an Index JAABE vol.1 no.2 November 2002 Kimiko Kohri 61 Fig.5. The Changes in the PMV, the Equipment Load and their Fig.6. The Changes in the PMV, the Equipment Load and Their Ranking during Heating Hours for 15 Years during the Ranking during Cooling Hours for 15 Years during the Winter Extreme Weather Days (in a south facing space) Summer Extreme Weather Days (in a south facing space) A demonstrates severe conditions for thermal comfort, it can then also be regarded as a considerably extreme and the extreme weather day of type C demonstrates weather day based upon the other indices of outdoor air severe conditions for the AHU load. The extreme weather temperature or enthalpy. The day that occurred before the day of type D demonstrates severe conditions for the selected day also tends to show characteristics of the con- FCU load, however the thermal environment in the pe- siderably extreme weather. rimeter zone does not deteriorate as much. These re- 2) During the heating season, the extreme weather day sults are the same as those obtained from the analysis of type B can be regarded as creating severe conditions performed for a south-facing office space. Further analy- from the standpoint of thermal comfort, AHU load, and sis for other location may be needed in order to validate FCU load when the daily average of the outdoor air tem- these results for the summer extreme weather. perature is at the minimum for 15 years. This result was obtained from the analysis of the case with a south- 6. Conclusions facing space, as well as in the case with a north-facing 1) By selecting the most extreme weather day based upon space. one of the indices of outdoor air temperature or enthalpy, 62 JAABE vol.1 no.2 November 2002 Kimiko Kohri 0.5 Perim eter zone Interior zone -0.5 Perim ete zone 5% 2.5% 1% 0.1 Interior zone 0.01 10 12 14 16 18 10 12 14 16 18 10 12 14 16 18 Time Time Time Aug. 3 1994 Aug. 7 1994 June 24 1991 (a) The PM V and its ranking 150 600 100 400 AHU 50 200 FCU 0 0 5% FCU 2.5% 1% 0.1 AHU 0.01 10 12 14 16 18 10 12 14 16 18 10 12 14 16 18 Time Time Time Aug. 3 1994 Aug. 7 1994 June 24 1991 (Ty pe A) (Ty pe C) (Ty pe D) The daily maximum The daily av erage The daily total of solar of outdoor air temp. of outdoor air radiation on w est w as at the max imum enthalpy w as at surface w as at the during cooling the max imum max imum during s easons. during cooling cooling seasons. seasons . (b) The equipment load and its ranking Fig.7. The Changes in the PMV, the Equipment Load and Their Fig.8. The Changes in the PMV, the Equipment Loads and Their Ranking during Heating Hours for 15 Years during the Ranking during Cooling Hours for 15 Years during the Winter Extreme Weather Days (in a north facing space) Summer Extreme Weather Days (in a west facing space) maximum, creates severe conditions for FCU load, al- 3) During the cooling season, the extreme weather days though the thermal environment on this day can be ex- of type A and B can be regarded as creating severe con- pected not to deteriorate so much. These results were ditions for thermal comfort only. The extreme weather obtained from the analysis of those cases involving a day of type A is that when the maximum of the daily south and a west-facing space. outdoor temperatures is at a maximum for 15 years. In this paper, the effects of extreme weather were The extreme weather day of type B is likewise that when analyzed in south-facing, north-facing and west-facing the average of the outdoor air temperatures is at a maxi- office spaces. Further study is planned in various cases mum for 15 years. The extreme weather day of type C, to clarify the effects of extreme weather dependent upon when the average of the outdoor air enthalpy is at the the building factors such as window ratio, glazing, in- maximum, causes severe conditions for the AHU load. sulation and space depth as well as the system factors The extreme weather day of type D, when the daily such as zoning and method of cooling and heating. total of solar radiation on the window surface is at its JAABE vol.1 no.2 November 2002 Kimiko Kohri 63 Ranking of large load [%] AHU load (W/m2) Ranking of w arm env ironmrnt [%] PMV FCU load (W/m) References 1) AIJ (2000) Expanded AMeDAS Weather DATA, maruzen 2) ASHRAE Handbook (2001) Fundamentals, 27.1-27.5 3) Colliver, D. G. and Gates, R. S. (1998) Sequences of Extreme Temperature and Humidity for Design Calculations, ASHRAE Transactions, Vol. 104, Part 1A, 133-145 4) Ishino, H. et al. (2002) Research on the Characteristics of Design Weather Data Derived from 15 Years of Thermal Load Simulations, Proc. Int. Conf. on CCEB, Paper No. 135 5) Ishino, H. (2001) A Proposal for an Estimation Method of Thermal Load and Space Radiant Environment for HVAC Sys- tem Design Developed by Applying DOE Technique, Proc. 7th Int. IBPSA Conf., Vol. 2, 1001-1016 6) Kohri, K. and Ishino, H. (1986) A Study on Total Evaluation Method of Thermal Environment and Energy Consumption, Transactions of AIJ, No.365, 40-48 7) SHASE (2001) Handbook of Heating, Air-Conditioning and Sanitary Part 3, Maruzen, 19-27 8) SHASE (1989) Estimation Method of Thermal Load for Heat ingand Air-Conditioning System Design, Maruzen, 3-13 64 JAABE vol.1 no.2 November 2002 Kimiko Kohri
Journal
Journal of Asian Architecture and Building Engineering
– Taylor & Francis
Published: Nov 1, 2002
Keywords: extreme weather day; thermal comfort; equipment load; expanded AMeDAS weather data; office space
