thermal performance of a multistoried residential apartment

Transcription

International Journal of Emerging Technology and Advanced Engineering
Volume 3, Special Issue 3: ICERTSD 2013, Feb 2013, pages 321-328
An ISO 9001:2008 certified Int. Journal, ISSN 2250-2459, available online at www.ijetae.com
THERMAL PERFORMANCE OF A MULTISTORIED RESIDENTIAL
APARTMENT IN WINTER SEASON AT KOLKATA
Soumyendu Biswas1+, Debasish Chowdhury2, Amitava Roy3, YG Yohanis4, Subhasis Neogi5
1,3
4
Bengal Engineering And Science University, Shibpur, India
School of the Built Environment, University of Ulster, Jordanstown campus, Shore Road,
Newtownabbey, Co. Antrim, BT37 0QB, United Kingdom.
2,5
School of Energy Studies, Jadavpur University, , Kolkata- 700032, India
+
Corresponding author email: [email protected]
ABSTRACT
The present study aims to analyze the thermal characteristics of a multistoried residential building in the winter
months. It is observed that the orientation of the apartment plays a vital role in the internal ambience of the space. The
reason behind is the building shell is exposed to diurnal variation of solar flux and also to the cyclic change in the
ambient temperature profile. The indoor air is noted to reach a delayed peak temperature as compared to outdoor peak
ambient temperature. This is caused due to the thermal inertia of the system. The solar heat gain by the structural
components slowly propagates into the building system as well as radiated towards the open sky. Such an effect
causes to rise in indoor air temperature. The various factors like construction materials, external colour, indoor
wall/ceiling colours etc. are found to influence the indoor environmental situation of the space. In the present study a
single building is considered with individual flats at different orientation but having uniform construction materials,
outer shading etc. So this study emphasizes on orientation and the exposed surface only.
Key words: Solar flux, data logging, thermal inertia, temperature profile and orientation.
1. INTRODUCTION
Thermal performance of multistoried residential
apartment is a matter of concern in warm–humid and
hot-dry climate. Research performed for improving
thermal comfort in non-conditioned building in hot
humid climate of Bankok by Atch Sreshthaputra [1].
Studies were made by Enedir Ghisi et. al. [2] in
Southern Brazil to assess the thermal performance of
bedrooms in different orientation in a multistoried
residential building located in Florianopolis, Brazil.
Studies were reported on energy-efficient building
envelop design for East Africa by Israel Da Silva et. al.
[3] where some basic energy-saving techniques have
been recommended to reduce building energy
consumption. A comparative analysis has been done
on the thermal performance of non air-conditioned
buildings with a vaulted roof and a flat roof under
different climatic conditions in the study of R. Tang et.
al.[4]. A study was performed by G. Barrios [5] where
it was found that in an air-conditioned room the most
important physical property of the wall / roof is its
thermal conductivity, which has to be as small as
possible, while for the non air-conditioned room the
most important physical property is the thermal
diffusivity, which also has to be as small as possible.
As per ASHRAE (1990b), energy resources are
fundamental ingredients of all the economic systems.
Presented at International Conference on Energy Resources and
Technologies for Sustainable Development, 07-09 February
2013, Howrah, India.
Efficient use of energy is important since the reserve
of our global energy resources is finite and depleting.
Energy use in building involves the parameters
which are complex and diverse in nature. Design of
energy efficient building is still not widely encouraged
and suffers by lack of appreciation for different
reasons. Guided by the market forces, many architects
even never bother to design the buildings considering
the climatic constrains and focus mainly on the
aesthetic aspects, sometimes even follow the negative
effect of technology. The building sector plays an
important role in the energy consumption. According
to the Earth Trends Country Profile 2003, the Indian
residential sector consumes about 201,000 mtoe.
(million tons of oil equivalent), which is about 11% of
world’s energy consumption in residential sector [6].
It is noted that in the residential and commercial
sector, there has been a rapid increase in the
consumption of electricity at a rate of about 13.2% [6].
Growing electrification and more comfortable style of
living have been the main causes of this increase.
India has a trend of having high-rise multi-dwelling
apartments in places of earlier detached houses. Due to
scarcity of land and need of open spaces through
minimum ground coverage – the present trend of highrise structures are predominant for all big Cities and
Metros of India.
ICERTSD2013-11-302
© IJETAE2013
Int. J Emerging Technology and Advanced Engineering
ISSN 2250-2459, Volume 3, Special Issue 3: ICERTSD 2013, Feb 2013, pages 321-328
4. STUDY AREA
Kolkata [Latitude: +22.57 (22º34’12” N),
Longitude: +88.36 (88º21’36” E)], the city in reference
is the state capital of West Bengal and most important
city of Eastern India. The city, having warm–humid
climate has the annual mean temperature as 26.8ºC
(80.2ºF) and monthly mean temperatures as 19ºC to
30ºC (66ºF to 86ºF). Summers (March – June) are
warm with temperatures above and around 30ºC;
during dry spells, maximum temperature often exceeds
40ºC (104ºF) in May and June [8]. Winter lasts for
only about two-and-half months to three months, with
seasonal lows dipping to 9°C to11°C (48° F to 52° F)
in December and January.
May (daily temperatures 27oC–37°C) is the hottest
month; January (12oC–23°C) is the coldest month. The
highest recorded temperature is 43.9°C, whereas the
lowest is 5°C [8]. The city receives 2,528 hours of
sunshine per year, with maximum sunlight exposure
occurring in March [9].
In the urban areas, these multi-storied apartment
buildings have major share in residential
accommodations. The individual flats / apartment
units of these buildings differ from each other in
respect of orientation, openings, shading, exposed
external surface etc. leading them to respond
differently in terms of thermal behavior.
The factors controlling the comfort within a building
are air temperature, mean radiant temperature,
humidity and air-flow. Kolkata, having predominantly
warm-humid climate, experiences a mild winter for
nearly three months in a year. It is also important to
study the thermal performance of the buildings in such
winter condition. This field of research is important as
the energy consumption of a building is associated
with its thermal performance over the entire year and
also the indoor thermal environment in the early
summer has a carry-over effect of the previous winter
due to thermal inertia of the building envelop.
Heat exchange processes at a building, being
considered as a defined unit, with the outdoor
environment has been expressed as follows and are
described by O. H. Koenigsberger et. al. [7]
The thermal balance of a system can be expressed
as: Qi + Qs ± Qc ± Qv ± Qm – Qe = 0
where Conductance (Qc) = A x U x T, Solar Heat
Gain(Qs) = Aw x I x θ, Ventilation Rate(Qv) = Cpv x V x
T
5. EXPERIMENTAL EVALUATION
5.1 Data Collection:
Period of Data Collection:
Nov’11 to Feb’12:
Room-temperature of the study building and
ambient temperature were monitored for 3 sets of data
for 92 days in 4 months:
1. 01.11.11 to 17.11.11 - 17 days
2. 12.12.11 to 12.01.12 - 32 days
3 16.01.12 to 27.02.12 - 43 days
Total 92 days
Five nos. of micro Data Loggers were used to record
the temperature data in different situations and
locations. In order to avoid errors due to different
response from each data loggers, those were calibrated
when all the data loggers were programmed to register
air temperature for every ten minutes over a period of
15 days (19.11.11 to 03.12.11) and were placed side by
side on a wooden platform at height of around 8ft.
from the floor in a room. The data were downloaded
and graphs were drawn from it. Graph generated from
the results of one logger was taken as reference and
others were found to be in parity with that.
2. The SCOPE and OBJECTIVE of the work
The proposed scope and objectives of the study are:
i.
To identify the parameters influencing the
indoor
thermal
characteristics
of a
multistoried residential buildings in the winter
months.
ii.
To identify the relative weightage of these
parameters influencing the thermal condition
of the space.
iii.
To compile and develop a database with
reference to parametric variations for the
design in warm-humid climate like kolkata.
3. METHODOLOGY
The study is to be undertaken in the following parts:
i.
To study and explain the problems and
important aspects of internal thermal
characteristics of a space.
ii.
To measure the temperature of the indoor
environment of different rooms (with different
orientation and outer envelope) of a
multistoried building in Kolkata and the
corresponding ambient temperatures.
iii.
To identify the temperature differences
between the indoor and the outdoor condition
and the reasons behind it. Also to identify the
time lag or phase shift and reasons behind it
for different situations occurred due to
periodic heat flow.
© IJETAE2013
5.2 Case Study
A three storied building in Southern part of Kolkata,
West Bengal, India is taken for the case study.


Floor height of the building: 3.0 meter. (clear)
Total height: 10.75 meter. (including parapet)
Fig.1 and Fig.2 show the south and east side view of
the building respectively. Fig.4 and Fig.5 show the
sectional and plan view of the building respectively.
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ICERTSD2013-11-302
Fig.1. South Side View
Fig.4. Sectional View
Fig.2. East Side View
Fig.3. Stevenson Screen for outdoor ambient
temperature measurement
© IJETAE2013
Fig.5. Floor Plan of the Building
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ICERTSD2013-11-302
19mm.ext.
plaster
Fig.6. The Construction details of the building(details of roof slab, intermediate slab, external wall and internal wall)
5.3 ANALYSIS
From the extensively collected data of four months,
five sets have been chosen as representative data for
the present purpose. They have been plotted and
analyzed.
For the first set of data, the data loggers were placed
as follow:
1. On the roof top (within Stevenson Screen)
2. In the room at S-W corner of 2nd. Floor
3. In the room at N-E corner of 2nd. Floor
4. In the room at S-W corner of 1st. Floor and
5. In the room at N-E corner of 1st. Floor
Due to the thermal capacity of the envelope, the
incident solar flux is absorbed by the surface of the
building system depending on the composition of
building envelop and thermal characteristics of the
construction materials. This in turn results in a time
delay for the heat to propagate into the system.
Actually, outdoor temperature will reach its peak
and will gradually cool down slowly, but the inside
wall temperature will keep rising gradually and will
reach its peak at a later time. The Heat is thus stored
within the building material and slowly propagates into
the system. The direction of the flow of heat is
dependent on both the boundary temperature such as
indoor air temperature and ambient air temperature.
When the outdoor temperature drops below that of
indoor, the heat flow direction is reversed.
It is observed that the S-W 2nd floor experiences a
greater temperature rise as compared to the S-W 1st
floor and N-E 2nd floor. This characteristic implies that
the heat transfer through the south and west exposed
walls and roof are the major paths of structural heat
gain.
It is observed that for the N-E location the heat gain
through the walls becomes insignificant and thus the
space remains cooler due to less amount of solar heat
gain. This is quite significant for the N-E 1st floor
location. The conduction impact of roof as well as that
of S-W walls is absent there.
As reflected in Fig.8, the ambient temperature in
this period ranges between 15.5ºC to 26.2ºC. It is
observed that for the S-W location, the 1st floor reaches
a higher temperature as compared to the 2 nd floor.
However the N-E location observed to attain lowest
indoor temperature.
The diurnal temperature fluctuation being between
15.5ºC and 26.2ºC the S-W 1st floor shows a lesser
temperature fluctuation during the cycle as
Fig.7. Time-Temperature Profile
The corresponding graph is shown here (Fig.7).
Here the ambient temperature is within the range of
22.5oC to 31.9oC. In general, the ambient heat enters
through the outer surface of the wall/roof.
© IJETAE2013
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ICERTSD2013-11-302
compared to the 2nd floor, the reason being the radiant
heat loss through roof slab resulting in lower indoor
temperature for the 2nd floor apartment.
On the other hand rooms of S-W side, receive more
solar radiation during a day cycle as compared to N-E
side. From Fig.8, it is observed that the N-E 2nd floor
experiences larger diurnal indoor temperature fluctuation
as compared to the 1st floor on the S-W location. This is
due to the fact that the N-E location has lesser amount of
structural heat gain and in most of the time the heat flows
out of the system due to lower ambient temperature.
However in case of the S-W location the heat flow
through building envelop to the indoor air is greater due
to solar heat gain of the exposed walls in the south as
well as west location. This, along with less heat loss
through intermediate floor slab leads to higher
temperature for the S-W 1st floor space.
From Fig.9, Fig.10 and Fig.11, it is observed that the
trend of ambient temperature fluctuation is identical;
however the ambient temperature has reached the lowest
value of about 11.75ºC as in Fig.9. Subsequently the
indoor temperature has also fallen around 17.1 ºC.
In Fig.10, it is observed that the impact of roof
radiation becomes predominant due to lower ambient
temperature. When the ambient temperature rose to
30.5ºC, S-W 2nd floor recorded highest temperature
(around 27ºC) of that day, higher than S-W 1st. fl. On
another day, as the peak ambient temperature rose below
26ºC, the room at S-W 1st floor recorded higher
temperature than its upper floor.
© IJETAE2013
From the Fig.9, Fig.10 and Fig.11 it is observed that in
all these cases, N-E 2nd floor shows lower indoor
temperature caused due to structural heat loss by the
building system. It is also observed that when the
ambient temperature falls below the range of 25 to 26º C,
the roof system starts loosing heat and thus 2nd floor
apartments (both N-E as well as S-W location) recorded
lower indoor temperature. However the S-W space was
found to have slightly higher indoor temperature and it is
due to the fact of the structural heat gain through walls.
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ICERTSD2013-11-302
On the other hand the maximum ambient temperature
(31.9oC)
occurred
at
12:30
hours
and
correspondingly the maximum indoor air temperature
rose to 28.7oC and 27.9oC for 2nd and 1st floor
respectively with a time delay of 2 hours 30 minutes and
1hour 10 minutes respectively. Thus it can be seen that a
thermal time lag of 1 hour 10 minutes to 2 hours 30
minutes prevails and it is due to the type of construction
and materials used.
In Fig.13, the minimum ambient temperature (19.3oC)
occurred at 06:20 hours whereas the minimum indoor
temperature was 22.4oC for 2nd floor and 24.4oC for 1st
floor at 07:40 hours and 10:10 hours respectively (i.e.
with a time delay of 1 hour 20 minutes to 3 hours 50
minutes).
6. PERIODIC HEAT FLOW AND TIME-LAG
While considering five representative days from above
five sets of data, one from each set, a clear view of Time
Lag or Phase Shift is obtained. The ambient diurnal
temperature variations and corresponding variations for
different apartment units are represented in Fig.12 to
Fig.15.
Again the maximum ambient temperature of 26.2oC
was recorded at 14:00 hours and correspondingly the
maximum indoor air temperature rose to 25.4oC and
25.8oC for 2nd and 1st floor respectively with a time delay
of 2 hours 50 minutes and 3hour 40 minutes respectively.
Thus it can be seen that a thermal time lag of 1 hour 20
minutes to 3 hours 50 minutes prevails.
In Fig.14 the upper and lower values of ambient
temperature have been recorded as 24.4oC and 11.8oC at
14:10 hours and 06:30 hours respectively. Corresponding
maximum and minimum temperature of 2nd floor went up
to 21.8oC and 18.0oC at 16:10 hours and 06:20 hours
respectively. Same for 1st. floor are 22.1oC and 19.5oC at
18:30 hours and 08:00 hours respectively. Thus thermal
time lags of 1 hour 30 minutes to 4 hours 20 minutes
have been recorded.
From Fig.12 it is observed that the minimum ambient
temperature (22.7oC) occurred at 03:00 hours however
the minimum indoor temperature of 25.8oC reached at
04:20 hours i.e. with a time delay of 1 hour 20 minutes.
© IJETAE2013
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ICERTSD2013-11-302
7. CONCLUSION
Flats/ individual units of the apartments for the cities
like Kolkata with predominant warm-humid climate have
the following criteria:
The top floor units having roof contact suffer
maximum, not only in summer (with high temperature
impact) but also in winter (with temperature lower than
the ambient). In this climatic condition with normal
construction trend i.e. 100 mm. thick RCC roof with
plain cement concrete roof tiles laid over 50 mm. thick
lime terrace, 250 mm. thick external brick work with 19
mm. external plaster and 12 mm. thick internal plaster,
the outward conductive heat flow has considerable
impact at an ambient temperature below the range of
24oC-25oC. However this can be modified with change in
construction specification.
Considering the orientation only, S-W side has the
maximum thermal impact. Roof has the maximum effect
on thermal conduction. For very high or very low
temperature the effect of roof is much more dominant
than the impact of orientation. In this climatic condition
with the above mentioned construction specification a
prominent thermal time lag prevails and it is due to the
type of construction and materials used and may be
modified with change in construction specification.
Results from Fig.15 also reflect the same trend of
thermal time lag.
Fig.16 reflects a situation where ambient temperature
is consistently lower than the indoor/room temperature.
8. ACKNOWLEDGEMENTS
The case studies have been carried out in the residence
of Mr. S. K. Biswas and Mr. U. Ghosh. Authors duly
acknowledge to all the family members of Mr. Biswas
and Mr. Ghosh for their kind support and permitting to
place the data loggers in their apartments.
© IJETAE2013
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ICERTSD2013-11-302
REFERENCES
[1] Sreshthaputra, A., May 2003, “Building Design and
Operation for Improving Thermal Comfort in Naturally
Ventilated Buildings in A Hot-Humid Climate”, Ph.D.
thesis, Texas A and M University.
[2] Ghisi, E. and Massignani, R. F., 2007, “Thermal
Performance of Bedrooms in a Multi-Storey
Residential Building in Southern Brazil”, Building and
Environment, 42(2): 730-742.
[3] Silva, I. D. and Ssekulima, E. B., 2011, “Energy
Efficient Building Envelope Design for Institutional
Buildings in East Africa”, paper on Energy Efficiency.
[4] Tang, R., Meir, I.A. and Wu, T., 2006, “Thermal
Performance of non air-conditioned buildings with
vaulted roofs in comparison with flat roofs”, Building
and Environment, 41(3): 268 – 276.
[5] Barrios, G., Huelsz, G., Rechtman, R.and Rojas, J.,
2011, “Wall/Roof Thermal Performance differences
between air - conditioned and non air - conditioned
rooms”, Energy and Buildings, 43(1): 219-223
[6] Singh, I. and Michaelowa, A., 2004, “Indian Urban
Building Sector: CDM Potential through Energy
Effiuciency in Electricity Consumption”, HWWA
Discussion Paper 289, Hamburg Institute of
International Economics.
[7] Koenigsberger, O. H., Ingersoll, T. G., Mayhew, A. and
Szokolay, S. V., Manual of tropical housing and
Building, Orient Longman.
[8] Canty and Associates LLC, April 2006, Weather Base
Entry for Kolkata.
[9] Gaia:Environmental
Information
System
(http://www.ess.co.at/GAIA/CASES/IND/CAL/CALma
in.html.)
AUTHOR BIOGRAPHY
Soumyendu Biswas, is an ArchitectTown Planner. He is now a research
scholar in Bengal Engineering and
Science University, Shibpur, Howrah,
India. He has research interest in
Energy efficient building technology,
Sustainable building planning and
Thermal efficiency of different building materials and
construction technology.
Debasish Chowdhury is M. Tech.
scholar at Department of School of
Energy Studies at Jadavpur University,
Kolkata, India. His specialzation is in
Solar Thermal Engineering, Building
Energy Management
and Biomass
Energy
Amitava Roy is Associate Professor
of Department of Architecture, Town
and Regional Planning at Bengal
Engineering and Science University,
Shibpur, Howrah, India. He has
research
interest
in
Thermal
Environment, Solar Architecture &
Passive Cooling.
Yigzaw Goshu Yohanis is professor
of Building Services Engineering at
the School of the Built Environment,
Centre for Sustainable Technologies
University of Ulster, Northern Island,
UK. His research interests are in the
field of Thermal energy, thermal
energy simulation, renewable energy
systems, long-term thermal energy storage, and human
energy behaviour. He has numerous publications in
International Journals.
NOMENCLATURE
Symbol
A
U
T
I
θ
Q
V
Cpv
Subscripts
v
c
s
i
m
e
w
© IJETAE2013
Description
Surface area
Thermal Transmittance
Temperature difference
Radiation heat density
Solar gain factor of
window glass
Heat flow rate
Ventilation rate
Volumetric Specific Heat
of air
Unit
(m2)
(W/m2deg C)
(C)
(W/m2)
Subhasis Neogi is Professor at School
of Energy Studies at Jadavpur
University, Kolkata, India. He has 25
years of teaching experience and 5
years of industry experience. He has
research interst in Energy Conservation
& Management, Energy Efficient
Buildings, Wind Energy, Solar Thermal Engineering etc.
He has several publications in various national and
international journals.
(W)
(m3/s)
J/(m3deg C)
Ventilation
Conduction
Solar Heat Gain
Internal Heat Gain
Mechanical Gain/ Loss
Evaporative loss
Window Area
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ICERTSD2013-11-302

thermal performance of a multistoried residential apartment

Transcription

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