BUILDING SPACE HEATING THROUGH MODIFIED TROMBE WALL: AN EXPERIMENTAL STUDY
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1 Proceedings of STME-2013 International conference on Smart Technologies for Mechanical Engineering 25-26 Oct 2013 BUILDING SPACE HEATING THROUGH MODIFIED TROMBE WALL: AN EXPERIMENTAL STUDY Shiv Lal * Centre for Energy Studies Indian Institute of Technology Delhi, India E-mail address: [email protected] S.C. Kaushik Centre for Energy Studies Indian Institute of Technology Delhi, India E-mail address: [email protected] .in P.K. Bhargava Central Building Research Institute Roorkee, CBRI, India Email address: [email protected] Nagesh Babu Balam Central Building Research Institute Roorkee CBRI, India Email address: [email protected] ABSTRACT This investigation deals with the performance evaluation of modified Trombe wall used for space conditioning. The modified Trombe wall comprises of two parts: (i) black painted mild steel plate of 3mm thickness, used as absorber, and (ii) metallic box of mild steel sheet filled with normal air, which was used as thermal storage. The experiment was conducted during winter season of 2012 at Central Building Research Institute Roorkee. Metallic box increases normal room temperature by 5.0 – 8.5˚C during daytime and by 2.0 -5.0˚C during night times. On the other hand, the metallic plate increases the room temperature by 1-4˚C above ambient air during night time. The ordinary Trombe wall increases the room temperature by 0.4-2˚C during the day time and 2-3˚C during night time temperature. The Experimental room temperature is alw ays higher than the reference r oom. There is lot of scope for conservation of energy in space heating, and the comfort room temperature can be achieved by metallic plate type or metallic box type sol ar chimney. Keyword: Trombe wall, space heating, modified Trombe wall 1. INTRODUCTION The utilization of solar energy for space heating is not a new concept though its use is increasing day by day due to expensive conventional energy resources. During the Stone Age, the solar energy was stored by thick stone wall during daytime in many cold regions across the globe which was used for heating purposes during night times. Trombe wall which is extensively used for heating, cooling and ventilation of modern building now days, it has been identified as an alternative for the thick masonry wall which is little bit costly. Trombe wall was developed by Trombe and Michel [1960] at the C.N.R.S. laboratory in France for the first time and thereafter, it was used for heating the buildings by p assive mode. There are number of researchers and scientists who have found Trombe wall very useful and effective for both heating and ventilation of buildings (Bansal 1993; Khedari 2000; Ong and Chow 2003, Darori 2004 and Zhai et al. 2005). Agrawal (1989) reviewed four different passive and active systems which were used extensively in building for natural heating and cooling. The concept of heat storage wall was introduced for heating purposes in the building during winter season initially, which later on also helped to reduce dependence on conventional resources of energy. Kaushik and Kaul (1989) developed a thermal model to study the thermal comfort in building by introducing mixed concrete-water thermal mass storage wall. Parametric study of passive cooling system in building was worked out by Gan (1998). His study revealed that the ventilation rate also increases with increase in the inlet and outlet opening dimensions with respect to the channel width. It was proposed that the interior surface of room wall should be insulated to enhance the ventilation rate in summer so that Trombe wall can be used both for heating and cooling of buildings. Sharma et al. (1989) conducted an experiment on a Trombe wall and found potential application of such a wall in solar passive building architecture in composite climatic conditions. Torcellini and Pless (2004) physically analyzed the Zeon visitor’s Centre and site entrance building situated at NREL wind site. The SEB Trombe wall has claimed as 10-41 cm thick single or double glass, south facing and having 2 -5 cm air gap of between glass c over and absorber surface. The selectiv e coating was used on surface to improve i ts performance. It was observed after two year’s study that Trombe wall was contributing 20% of the total heating provided to the building with the avera ge efficiency of the wall be ing 13%. Burek and Habeb (2007) investigated the air flow and thermal efficiency characteristics of both solar chimney and Trombe walls. Chel et al. (2008) estimated the passive heating potential of Trombe wall for honey storage building by using TRNSYS and concluded that the energy conservation up to 3312kWh/year can be achieved by making assumption of a short simple payback period like seven months.
Transcript of BUILDING SPACE HEATING THROUGH MODIFIED TROMBE WALL: AN EXPERIMENTAL STUDY
8/12/2019 BUILDING SPACE HEATING THROUGH MODIFIED TROMBE WALL: AN EXPERIMENTAL STUDY
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Proceedings of STME-2013International conference on Smart Technologies for Mechanical Engineering
25-26 Oct 2013
BUILDING SPACE HEATING THROUGH MODIFIED TROMBE WALL: ANEXPERIMENTAL STUDY
Shiv Lal* Centre for Energy Studies
Indian Institute of Technology Delhi, IndiaE-mail address: [email protected]
S.C. KaushikCentre for Energy Studies
Indian Institute of Technology Delhi, IndiaE-mail address: [email protected]
P.K. BhargavaCentral Building Research Institute Roorkee,
CBRI, IndiaEmail address: [email protected]
Nagesh Babu BalamCentral Building Research Institute Roorkee
CBRI, IndiaEmail address: [email protected]
ABSTRACTThis investigation deals with the performance evaluation ofmodified Trombe wall used for space conditioning. Themodified Trombe wall comprises of two parts: (i) black paintedmild steel plate of 3mm thickness, used as absorber, and (ii)metallic box of mild steel sheet filled with normal air, whichwas used as thermal storage. The experiment was conductedduring winter season of 2012 at Central Building ResearchInstitute Roorkee. Metallic box increases normal roomtemperature by 5.0 – 8.5˚C during daytime and by 2.0 -5.0˚Cduring night times. On the other hand, the metallic plateincreases the room temperature by 1-4˚C above ambient air
during night time. The ordinary Trombe wall increases theroom temperature by 0.4-2˚C during the day time and 2-3˚Cduring night time temperature. The Experimental roomtemperature is always higher than the reference room. There islot of scope for conservation of energy in space heating, and thecomfort room temperature can be achieved by metallic platetype or metallic box type solar chimney.
Keyword: Trombe wall, space heating, modified Trombe wall
1. INTRODUCTIONThe utilization of solar energy for space heating is not a newconcept though its use is increasing day by day due to
expensive conventional energy resources. During the StoneAge, the solar energy was stored by thick stone wall duringdaytime in many cold regions across the globe which was usedfor heating purposes during night times. Trombe wall which isextensively used for heating, cooling and ventilation of modernbuilding now days, it has been identified as an alternative forthe thick masonry wall which is little bit costly. Trombe wallwas developed by Trombe and Michel [1960] at the C.N.R.S.laboratory in France for the first time and thereafter, it was usedfor heating the buildings by passive mode. There are number ofresearchers and scientists who have found Trombe wall veryuseful and effective for both heating and ventilation of
buildings (Bansal 1993; Khedari 2000; Ong and Chow 2003,Darori 2004 and Zhai et al. 2005).Agrawal (1989) reviewed four different passive and activesystems which were used extensively in building for naturalheating and cooling. The concept of heat storage wall wasintroduced for heating purposes in the building during winterseason initially, which later on also helped to reducedependence on conventional resources of energy. Kaushik andKaul (1989) developed a thermal model to study the thermalcomfort in building by introducing mixed concrete-waterthermal mass storage wall.Parametric study of passive cooling system in building was
worked out by Gan (1998). His study revealed that theventilation rate also increases with increase in the inlet andoutlet opening dimensions with respect to the channel width. Itwas proposed that the interior surface of room wall should beinsulated to enhance the ventilation rate in summer so thatTrombe wall can be used both for heating and cooling ofbuildings. Sharma et al. (1989) conducted an experiment on aTrombe wall and found potential application of such a wall insolar passive building architecture in composite climaticconditions.Torcellini and Pless (2004) physically analyzed the Zeonvisitor’s Centre and site entrance building situated at NRELwind site. The SEB Trombe wall has claimed as 10-41 cm thicksingle or double glass, south facing and having 2 -5 cm air gap
of between glass cover and absorber surface. The selectivecoating was used on surface to improve its performance. It wasobserved after two year’s study that Trombe wall wascontributing 20% of the total heating provided to the buildingwith the average efficiency of the wall being 13%. Burek andHabeb (2007) investigated the air flow and thermal efficiencycharacteristics of both solar chimney and Trombe walls. Chel etal. (2008) estimated the passive heating potential of Trombewall for honey storage building by using TRNSYS andconcluded that the energy conservation up to 3312kWh/yearcan be achieved by making assumption of a short simplepayback period like seven months.
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More recently, Jaber and Ajib (2011) optimized a Trombe wallfor Mediterranean region by using life cycle cost criterion andresults were simulated by TRNSYS and concluded that theoptimum Trombe wall area ratio from thermal and economicalpoint of view should be 37%. This optimum ratio has reducedlife cycle cost (LCC) by 2.4% and CO2 is reduced annually by445 kg.
In the present investigation we have designed a ModifiedTrombe wall/solar chimney for building space heating in winterseason at CBRI Roorkee with the concept of increasing the walltemperature by application of metallic sheet. This will lead todevelop an approach for designing a Trombe wall in coldregion of India and in North hemisphere.
2. System DescriptionThe built up modified Trombe wall/ solar chimney is designedfor a specific room having 16.253 m3 volume situated at CBRIRoorkee, India [Latitude 29º 51’ and Longitude 77º 53’ at 274m mean sea level] as illustrated in Figure 1. The design wasbased on 4.0 ACH at annual average solar insolation about400W/m2. The area of inlet and exit vent was kept same as 0.09m2. The vertical gap between inlet and exit vent from the centerpoint is about 2.85 m. There is a vast gap in available literatureon application of a metallic absorber for space heating throughthe solar chimney.This modified solar chimney / Trombe wall is capable toaccommodate the effect of metallic plate and metallic box typeabsorber. Another important feature introduced in this systemis, as hinged glass cover frame from the center by which it canbe tilted to any angle. This feature gives an optimum tilt angleto increase the performance and reduce the back flow in thechimney which is essential in summer season, which generatesstack’s effect and measurable flow. To control the space
heating and ventilation features of a building, two hingeddampers are provided at the top of the frame.The modified Trombe wall constructed in two parts, in the firstone, a metallic sheet (3 mm thickness) is fixed over a woodenframe 0.9 m x 2.55m x 0.045m, and the second part is made ofmetallic box having equal dimension to wooden frame asshown in Figure 2. To assess the temperature profile of thedesigned Trombe wall, thermo-couple was placed at differentpositions (see Figure. 2). The plan of experimental room,reference room and thermocouple position in same is shown inFigure 3.Both the plate and water wall are painted by nickel chromeblack paint for increasing the absorptivity up to 80%.
Figure 1: Modified Trombe wall for building space heating
Figure 2: Orthographic view and dimensions of modifiedTrombe wall
Figure 3: Plan of Experimental and reference room
3.
Instrumentation and Measurement
The experimental study was conducted during winter season ofyear 2012. The global and diffuse solar radiations incident on ahorizontal surface were measured by Solar Pyranometer(Modle: SP Lite2 type; Make: Eppley, Netherlands), and(Modle: SP Lite2 type; Make: Kipp&Zonen, Netherlands)respectively is shown in Figure 4 (a, b). Calibrated T-typethermocouples connected to a multi-channel temperature datalogger (Digitec, India) was used to measure the airtemperatures and data logger for solar insolation andtemperature recording are shown in Figure 4(c, d). Totalexperimental uncertainties of different parameters measuredduring the experimental work on the modified Trombe wall/solar chimney.
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Figure 4: Measuring equipment (Pyranometer and data logger)
4. Result and Discussions:
4.1 Observation and measurement of Environmental
Parameter:
The environmental parameters such as global, diffuse solarradiation, and ambient air temperature were monitored fortwenty five days in December 6-30, 2012. The typical day ofDecember is on 10th day of the month as suggested by (Duffyand Beckman, 1980). The Figure 5 reveals the relationbetween global, diffuse solar radiation, and ambient airtemperature of typical day of December month. It was found
that the maximum global radiation was about 576.25 W/m2 at12:00 hours, whereas the maximum diffuse solar radiation wasabout 109.34 W/m2 at 11:00 hours. As far as the ambient airtemperature is concern, it was maximum as 20.1˚C at 13:00hours and minimum as 3.2˚C at 7:00 hours.
Figure 5: Solar radiation for the average day of December,2012
4.2 Comparative study of simple and modified Trombe
wall
The temperature profile of simple and modified Trombe wall isdepicted in Figure 5. The figure reveals that the ambient airtemperature found lower from 6:00 PM to 9:00AM and it isfound higher than the reference room temperature for otherperiods. The lowest ambient air temperature was observed as3.2˚C (Below 4˚C freezing started) at 7:30 AM on 10 th December and on other days also, ambient air temperature wasrecorded lowest in morning hours. The space heating effectthrough Trombe wall is shown in Figure 6 and 7.
Figure 6: Full day Variation of Different temperatures for
average day of Dec 2012
Figure 7: Comparison of experimental room, reference room
and ambient air temperature
The experimental room temperature was observed higher thanthe ambient air and reference room temperature that is becauseof low losses and more heat stored during day time. Thereference room temperature (without wall heating) was foundlower than the ambient air temperature during day time, but theexperimental room temperature was found approximately 2-9˚C
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higher for various set up times. The difference between roomand ambient temperatures in least morning hours was recordedhigher as compared to other median times. Experimental roomtemperatures were recorded 1.5-8˚C higher with reference roomin peak winter season.
The temperature of black masonry wall (simple Trombe wall)
was recorded lower than the both metal plate and metallic box.And as a result of that the room temperature increases in orderof wall, metal plate and metallic box which is clearly shown inFigure 8. It was observed that, the higher the absorbertemperature, more the convective effect. On the other hand theoutput air temperature through Trombe wall was found higherfor metallic box as compared to others.
Figure 8: Comparison of Simple black masonry wall, MS plate,
and MS box data in Trombe wall
4.3 Temperature variation according to height of absorber
The temperature is not constant throughout the entire height ofabsorber plate which is clearly shown in Figure 9. It revealsthat, the lower temperature found at the lowest end of absorberbecause absorber plate end is in contact with room temperature.On other hand the temperature at height of 2.55m reducesslightly from the maximum temperature (at 1.8m) because thisend also is in contact with room air and hot air bends (eddyformation at the corner of 90 degree bend). It expressed that theair flow temperature increases with increase in chimney height.
Figure 9: Temperature variation according to height of absorberplate at 12:00 hour on typical day
4.4 Error and uncertainty analysis
There is chance of error or uncertainties during the experimentsand this may be due to, instrumentation (data logger, memory,electronic circuit, transmitters, wire resistance etc.), type of
junction and sensor, climate condition, calibration method,method of observation and testing methods for evaluation. Thetotal experimental uncertainties of different parametersmeasured during the experiment on modified Trombe wall werepresented in Table 1. Table 1: Uncertainties of the experimental parametersParameters Units Uncertainty
Uncertainty in the temperaturemeasurement (T-typethermocouples used)
˚C
Uncertainty in the solar energymeasurement
W/m2
5. Conclusions:
The effect of metallic plate and metallic box on space heating
of building in peak winter season was evaluated. It was found
that the technology introduced in modified Trombe wall having
better performance as compared to conventional Trombe wall.
The experimental results were compared with reference room
where no external space heating is provided. After inducing
metallic box in Trombe wall the temperature during night time
was higher by 5-10˚C corresponding to ambient air
temperature. On the other hand, during the day time the room
temperature was 2-5˚C higher than ambient air temperature.
The conventional Trombe wall gives higher temperature by 0.4-2˚C during day time whereas; it was 2-3˚C during night time
corresponding to ambient air. The metallic plate heating effect
gives the 1-4˚C temperature above ambient air temperature
during night time and 2-3˚C during day time. The experimental
room temperature recorded 1.5-8˚C higher with reference room
in peak winter season. These technologies found suitable for
producing the comfort room temperature.
On the other hand metallic plate temperature increases with
increase in solar radiation and accumulated heat was enough to
produce chimney effect, the air temperature inside the chimney
was increased from lower side to upper side. The platetemperature found higher at the upper stage as compared to
lower and middle stage, it clearly indicates convective heat
transfer at upper level is less than the lower side.
The temperature of air near to metallic plate is higher and it
decreases towards glazing side but near to glazing air
temperature is slightly higher. The air extracts convective heat
from both plate and glazing.
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ACKNOWLEDGMENTSThe author (Shiv Lal) gratefully acknowledges UniversityCollege of Engineering, Rajasthan Technical University, Kota,Rajasthan (India) and IIT Delhi (India), for sponsorship underquality improvement program of government of India.
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