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International Journal of Enhanced Research Publications, ISSN: XXXX-XXXX
Vol. 2 Issue 4, April-2014, pp: (1-4), Available online at: www.erpublications.com
Integrated Inbuilt Roof Cooling System (IIRCS):
Thermal Design Optimization and TechnoEconomic Analysis
Author Name: Vanita Thakkar1
Associate Professor, Mechanical Engineering Department, Babaria Institute of Technology, BITS Edu Campus,
Vadodra-Mumbai N H # 8, Varnama, Vadodara – 391 240.
Address (for correspondence) : “Devashish”, 317, Sahakarnagar, New Sama Road, Vadodara – 390 024
Abstract: There is increasing awareness the world round regarding energy-efficient, environment-friendly space
cooling systems. Such systems become more important in developing countries like India, having acute power
shortage problems, especially if they are cost-effective. Integrated Inbuilt Roof Cooling System (IIRCS) is a low
cost, energy efficient, easy-to-maintain and non-polluting Active Solar Architecture System having promising
prospects of use in rural and urban areas for residential/commercial buildings, cattle sheds, etc. in hot, dry
regions. In an IIRCS, heat, from solar radiant energy and internal heat-load from occupants, appliances, etc. is
carried away by coolant, water circulated through piping system laid in the roof called Roof Piping System (RPS)
and hot coolant is cooled in a heat exchanger. The coolant is re-circulated in RPS. The paper presents Thermal
Design Optimization of an IIRCS using a java-based Simulation Program for modeling a BPHE-based IIRCS for
a building, 10mx10m with horizontal roof, followed by Costing.
Keywords: Active Solar Architecture, Inbuilt Roof Cooling System, BPHE, ETHE, Thermal Design
Optimization.
Introduction
A substantial share of world energy resources are being spent on heating, cooling and lighting buildings, which are designed
to squeeze in as much as possible per sq. m. area due to rapid urbanization. Ensuring means of enhancing and maintaining
thermal comfort in buildings has thus become an important requirement. The emerging Energy-conscious Architectural
style, SOLAR ARCHITECTURE, aims at comfortable, energy efficient buildings. “Passive Solar Architecture” relies on
design of buildings based on natural thermal conduction, convection and radiation to ensure climate control. Vaastu
Shaastra – the ancient Indian guide to building a structure, according to specific principles, all of which are based on strong
scientific fundamentals, actually advocates what we call – Passive Solar Architecture. “Active Solar Architecture” involves
the use of solar collectors, which require an external source of energy. “Active features” are incorporated to ensure finer
control on the internal climate heat distribution. Active Solar Systems use means like solar panels and solar photovoltaics
for heat collection and electrically-driven pumps or fans to transport heat / cold to the space to be conditioned. In the
present scenario, with lots of space and planning constraints, a proper combination of Passive and Active Solar Architecture
– which gives “Hybrid Systems” – needs to be applied to ensure a comfortable, energy-efficient residence / working place
[1].
The paper introduces Integrated In-built Roof Cooling System (IIRCS). An IIRCS is a low cost, energy efficient, easy-tomaintain and non-polluting Active Solar Architecture System [2]. It has promising prospects of use in rural and urban areas
for residential / commercial buildings, cattle sheds, etc. in hot, dry regions. In an IIRCS, heat – due to solar radiant energy
and internal heat load due to occupants, appliances, etc. – is carried away by coolant – water – circulated through a piping
system laid in the roof – either in slab or in water-proofing – and the hot coolant is cooled in a heat exchanger – either
Buried Pipe Heat Exchanger (BPHE) or any other simple heat exchanger. The cooled coolant from heat exchanger is recirculated in the Roof Piping System (RPS). The paper presents Thermal Design Optimization [3] of an IIRCS using a javabased Simulation Program for modeling a BPHE-based IIRCS for a building – 10m x 10m area, having a horizontal roof –
followed by Costing [4], which involves :
1.
Roof Piping Analysis – Using an electrical analogy network to do Heat Transfer Analysis. A parametric study is
done for designing RPS laid in roof slab, which includes selection of pipe material and specifications and
computation of various parameters of the RPS.
2.
BPHE Analysis – to select best suited configuration and compute various parameters of the BPHE.
3.
Pumping Power Computations.
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International Journal of Enhanced Research Publications, ISSN: XXXX-XXXX
Vol. 2 Issue 4, April-2014, pp: (1-4), Available online at: www.erpublications.com
Literature Review
Three main categories of Non-Conventional Space Conditioning Systems can be identified –
1.
Solar-assisted air conditioning systems,
2.
Earth Tube Heat Exchanger (ETHE) / Buried Tube Heat Exchanger (BPHE) based Space Conditioning Systems
and
3.
Other non-conventional space conditioning systems.
There can be varieties in each type depending upon the geographic and climatic conditions for which they are developed,
the specific requirements of the system – like, residential building, work-place, greenhouse, auditorium, etc. as well as the
principle on which they are based and the technology they make use of [5].
The current paper focuses on the use of the second type of systems, the details regarding which are discussed in the
succeeding review.
It is a well-known fact that while ambient temperatures are subjected to diurnal, seasonal and annual fluctuations,
temperatures of the soil beyond a certain depth remain virtually constant. Though these variations do occur, amplitudes of
fluctuations in the deep soil temperatures remain much smaller than those at the surface. So, deeper layer of the soil can be
used as both – heat sink (during summer) and heat source (during winter) [2]. BPHE / ETHE Systems are low cost, reliable
and easy-to-maintain systems based on this concept. The coolant / heating fluid may be air or water or any other suitable
fluid and it is circulated with the help of a blower – when air is used – or a centrifugal pump – when water / liquids are used
– through an underground piping system – to reject the heat gained from the thermal load on the structure being cooled, or –
to gain heat from the ground to heat the structure [5].
Figure 1 shows outline of various ETHE / BPHE based space conditioning systems [5].
Figure 1 : Outline of various Earth Tube Heat Exchanger (ETHE) / Buried Pipe Heat Exchanger (BPHE) based space
conditioning systems.
Figure 2 shows a typical Earth-Air Heat Exchanger (EAHE) system, in which air is circulated through piping laid in the
ground and after being heated or cooled, as per the requirement / season, the air is circulated in the space to be conditioned
[6]. Figure 3 shows the working of Heat Pumps – commonly known as Geo-exchange or Geothermal systems, which are
double circuit systems and work on the principle of Vapour Compression refrigeration systems and are widely used in the
USA, Canada and European countries like Germany, Denmark, Finland, Sweden, etc. [7].
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International Journal of Enhanced Research Publications, ISSN: XXXX-XXXX
Vol. 2 Issue 4, April-2014, pp: (1-4), Available online at: www.erpublications.com
Figure 2: Typical Earth-Air Heat Exchanger (EAHE) System [6]
Figure 3 : Heat Pumps [7]
The other type of ETHE / BPHE based space conditioning system – Integrated Inbuilt Roof Cooling System (IIRCS) is
described in the succeeding discussions. A combination of EAHE and IIRCS is being used in the office building of a
company named Universal Medicap Ltd. (UML), Vadodara. The design of the Roof Piping System in the IIRCS at UML is
based on thumb rules and logic. A systematic study and analysis and implementation of its conclusions can help in
optimizing performance of the system [8].
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International Journal of Enhanced Research Publications, ISSN: XXXX-XXXX
Vol. 2 Issue 4, April-2014, pp: (1-4), Available online at: www.erpublications.com
Integrated Inbuilt Roof Cooling System (IIRCS) : System description
An Integrated Inbuilt Roof Cooling System (IIRCS) – an Active Solar Architecture System – consists of :
1.
Roof Piping System (RPS) – the thermal circuit on which it is based is shown in fig. 1.
2.
Heat Exchanger.
3.
Pump.
Figure 4 shows a schematic diagram of BPHE-based IIRCS. Figure 5 shows the thermal circuit diagram of the system
under consideration. Here, heat – due to solar radiant energy as well as internal heat load due to occupants, appliances,
etc. – is carried away by coolant – water – circulated through a piping system laid in the roof – either in slab or in waterproofing – and the hot coolant is cooled in a heat exchanger – either Buried Pipe Heat Exchanger (BPHE) or any other
simple heat exchanger. The cooled coolant from the heat exchanger is re-circulated in the Roof Piping System (RPS).
Figure 4 : Schematic Diagram of BPHE-based Integrated Inbuilt Roof Cooling System (IIRCS) [2]
Figure 5 : Thermal Circuit Diagram of Roof Piping System (RPS) [2]
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International Journal of Enhanced Research Publications, ISSN: XXXX-XXXX
Vol. 2 Issue 4, April-2014, pp: (1-4), Available online at: www.erpublications.com
Thermal Analysis of IIRCS
The thermal analysis of IIRCS involves the use of various theoretical and experimental models – predicting correlations,
based on investigations carried out by earlier investigators over the years. A model – based on Electrical analogy, shown in
figure 5 – is developed, using appropriate correlations for computing and estimating relevant parameters. A simple Javabased Simulation Program is developed for computation and analysis.
The thermal design of IIRCS can be divided into 3 important stages:
A. Roof Piping Analysis :
It involves:
1.
Estimation of Total Heat Load, which consists of :
a. Load from Solar Radiant Energy. [2]
b. Internal Load due to various sources like occupants, appliances, etc.
2. Assessment of various modes of heat transfer taking place on the Roof-Top as well as in the RPS, embedded in it
– with the help of Electrical Network Analogy.
3. Computing :
a. Optimum Pipe Center Distance from the Roof Surface.
b. Optimum Horizontal Distance between the pipes to obtain the required room temperature for the given
pipe specifications (d).
c. Outlet temperature of water (tfoc) – for given pipe length, which depends on the Roof Geometry.
d. The Room Temperature (ti,cal).
e. Number of pipes required in the RPS (Np) and the total mass flow rate of water (mtotal).
Initially, a segment of roof is considered, in which length of roof is equal to 1m – corresponding to 1m length of Coolant
Flow Pipe (CFP) laid length-wise in the roof. Width of roof is equal to the sum of twice the outer diameter of CFP and
horizontal distance between the edges of the two pipes under consideration (d). For given pipe specifications, a value of d is
assumed.
After computing the values of various thermal resistances, as shown in figure 5, the heat gained by water (qw) and the outlet
temperature of water can be computed with the help of Efficiency Factor (F’) – actual heat gain rate per pipe per unit length
to the gain, which would occur if the roof were at inlet temperature of water in the CFP (tfi) – and Heat Removal Factor (Fr) –
the ratio of actual useful heat gain rate to the gain, which would occur if the roof were at temperature, tfi everywhere [2].
These values will be for 1m length of CFP. Considering the outlet temperature at the end of first segment as the inlet
temperature for the next segment and adding up the heat gained by water in each segment, tfoc and total heat gained by water
across the length of the pipe, qw,total can be computed. The temperature of room (ti,cal) for the assumed value of d can be thus
found and it should match the value of required room temperature. If it is more, then the assumed value of d should be
reduced and calculations for the optimum horizontal spacing between the pipes (d opti) have to be repeated till the desired
value of room temperature (ti) is obtained and vice versa. Having known the dopti, Number of pipes required for the RPS, Np
and mass flow rate of coolant – water – mtotal required to be circulated through the RPS can be known. The heated water at
temperature tfoc goes through a header to the BPHE under gravity flow.
B. BPHE Analyasis :
It involves:
Computing Buried Depth – the depth below ground level, where a stable thermal environment is available and
where the BPHE has to be laid.
2. Computing the Length and Number of pipes required in BPHE and the distance between them – considering only
radial heat flow in one direction for buried pipe, there will be three resistances in series across the heat flow path :
a. Resistance to Convective Heat Transfer to water flowing through Buried Pipe (Rf’).
b. Conduction Resistance of the Pipe Material (Rp’).
c. Conduction Resistance offered by Soil (Rs’).
For a given velocity of water and mass flow rate required in RPS, there is a maximum possible number of pipes which can
be laid in the BPHE. A further increase in the number would cause the Reynold’s Number in the BPHE pipes to go below
1800, which makes the flow laminar and thus heat transfer performance will be lowered. Also, for a given velocity, the
length of pipe cannot be reduced beyond a certain limit. Knowing these two, a proper combination of length and number of
pipes can be obtained.
1.
Total Thermal Resistance of the circuit (Rtotal) is the sum of above three resistances. Assuming LMTD temperature variation
across the buried pipe, the radius of cylindrical soil layer surrounding the buried pipe is the only unknown parameter, which
can be found from the value of Rs’ – which can be computed by trial and error method. For an assumed length and number of
pipes of pipe specifications considered, if the value of Rs’ turns out to be negative, changes in pipe length and number can be
made such that Rs’ becomes positive and a proper combination of both parameters is obtained.
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International Journal of Enhanced Research Publications, ISSN: XXXX-XXXX
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The cooled water – at temperature tfi – gets collected in an underground tank and it needs to be pumped to the RPS. An
underground tank of appropriate size is constructed at buried depth and water from the BPHE pipes is considered to get
directly collected in the tank.
C. Pumping Computations :
It involves calculating, using usual hydraulics formulae:
1.
2.
3.
Suction Head.
Delivery Head.
Head losses due to friction, bends, valves, contractions and enlargements in the piping system, etc.
Thermal Design of IIRCS
In Thermal Design of IIRCS, attempt is made to one by one reach an optimum value of various parameters and further
design / analysis is carried out with values decided upon, in the succeeding sub-sections. Effects of variations in the
parameter under consideration in logically decided range, on various important system parameters are tabulated and
checked graphically and conclusions are drawn.
Thermal Design of IIRCS is based on the cooling load estimated on a Design Day – “A day when the dry bulb temperature
(DBT) and wet bulb temperature (WBT) peak simultaneously.” However, this does not normally happen. So, the maximum
DBT is considered. For Vadodara, maximum DBT is observed in the month of May and solar load on 15 th of May at 12
noon is considered maximum solar load during summer. The procedure of Thermal Design of IIRCS is divided into two
stages:
A. Thermal Design of RPS:
Table 1 shows the Thermal Design Input Data required for the design of RPS. A Horizontal Roof having dimensions – 10m
x 10m – is considered for study. Initially, the values of parameters are taken as shown in the table. The first parameter to get
optimized is vertical distance between Pipe Center and Roof Surface. Also, initially, it is assumed that the pipe is laid at the
center of the slab.
Table 1 – Thermal Design Input Data for Inbuilt Roof Piping System.
S. No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Input Parameter
Value
Location
Nature of Roof
Slope of Roof
Orientation of Roof
Ambient Air Temperature (oC)
Roof Surface Temperature (oC)
Emissivity of Roof Surface
Pipe outer diameter – do (mm)
Pipe Thickness (mm)
Thermal Conductivity of Pipe (W/m K)
Horizontal Distance between the pipes – d (mm)
Pipe embedded in (Water-Proofing / Slab)
Thickness of Roof Water-Proofing (mm)
Thermal Conductivity of Roof Water-Proofing (W/m K)
Thickness of Roof Slab (mm)
Thermal Conductivity of Concrete (W/m K)
Pipe Centre Distance from Roof Surface (mm)
Velocity of water in Coolant Flow Pipe (m/s)
Total Internal Load (W/m2)
Required Room Temperature – ti (oC)
Roof length (m)
Roof width (m)
Vadodara
Horizontal
0
Due South
42
60
0.92
29
2
40
To be found.
Slab
100
0.7
150
1.4
175
1
600
29
10
10
Table 2 shows the sequence of steps involved in the Thermal Design of RPS, along with the observations and conclusions –
in brief :
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Table 2 – Steps, Observations and Conclusions of Thermal Design of Roof Piping System (RPS).
S. No.
Step
Optimizing
Pipe
Center Distance from
Roof Surface (x in
mm).
Deciding
Pipe
Material.
1.
2.
3.
a)
Observation
RPS should be laid as close
to the Roof Surface as
possible.
Conclusion
x = (thickness of water-proofing) +
10 + [(pipe outer diameter) / 2].
Thermal Conductivity of
Pipe material does not
contribute significantly to
system performance.
Deciding Pipe Specification :
Deciding
Pipe
Pipe Thickness should be as
Thickness.
less as possible.
Pipe Material Chosen – HDPE
(thermal
conductivity
varies
between 0.4-0.51).
Deciding Pipe Outer
Diameter - dopti.
Effect of velocity of
water (vw) in RPS.
b)
4.
Pipe Outer Diameter should
be as less as possible.
dopti does not vary
considerably, tfoc decreases
till a certain point and mtotal
increases with increase in
vw.
Min. possible thickness to be
considered for the pipe outer
diameters considered.
16mm outer diameter, 1.5mm thk.
HDPE pipe selected.
Values of tfoc and mtotal influence
BPHE design and pumping power
requirements. So, vw can be decided
on the basis of length and no. of
pipes in BPHE and pumping power
requirements.
B. Thermal Design of BPHE and Estimating Pumping Requirements:
Water from RPS comes to BPHE (it is a set of pipes arranged parallel to each other at buried depth) for cooling, gets
collected in the Underground Tank and is pumped back to the RPS from there. The temperature of water at the inlet of
BPHE is the temperature of water at the outlet of RPS and the mass flow rate through the BPHE is the same as that
calculated for RPS. The temperature of water at outlet of BPHE would be the same as that required at the inlet of RPS or a
degree less than that.
Table 2 shows the input data for BPHE and Pump Calculations. vw is taken as 2 m/s, as the rate of variations in dopti, tfoc and
mtotal become negligible after this value of vw.
Table 3 – Input Data for BPHE and Pump Calculations.
S. No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Input Parameter
Temperature at buried depth (oC).
Surface Temperature (oC).
Initial Soil Temperature (oC).
Pipe Outer Diameter (mm).
Pipe Thickness (mm).
Thermal Conductivity of the Pipe material
(W/m K).
Pipe Length (m)
Pipe Number.
Roof Height (m)
Tank Depth (m)
Pump Efficiency (%).
12.
Roof Piping Inlet Header Inner Diameter
(mm)
13.
14.
Number of bends in roof piping.
R/D ratio of bends in the roof piping.
Value
25
42
22
16
1.5
0.51 (initially – same as that of roof piping).
To be found.
To be found.
4.5
2
85
Same as the Roof Piping Outlet Header
Diameter – computed in Roof Piping
Analysis.
6
1
The Table 4 shows the steps followed in this stage of design, along with the observations and conclusions – in brief :
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Table 4 – Steps, Observations and Conclusions in the Thermal Design of BPHE.
S. No.
1.
2.
a)
b)
3.
Step
Deciding
BPHE
Pipe
Material.
Observation
No. of pipes required in
BPHE
decreases
with
increase
in
Thermal
Conductivity
of
Pipe
Material.
Deciding Pipe Specification :
Deciding
BPHE Pipes should be as
BPHE
Pipe
thick as possible.
Thickness.
Deciding
Pipe OD should be as less as
BPHE
Pipe
possible
(i.e.
smallest
Outer
possible size of pipe with
Diameter.
maximum thickness should
be selected).
Deciding
Pumping Power Requirement
Pump
increases, min. length of
Capacity and
BPHE pipe decreases and
Velocity
of
max. permissible no. of pipes
water in RPS
increases with increase in vw.
(vw).
Conclusion
Pipe Material for BPHE – GI (easily
available, less costly and higher
thermal conductivity than HDPE and
SS.)
Max. possible thickness to be
considered for the pipe outer
diameters considered.
16mm outer diameter, 3mm thk. GI
pipe selected.
The decision regarding selection of
vw should be taken after taking in
consideration the space available for
laying BPHE and the cost factor. If
more space is available, longer pipes
can be laid, lesser vw and hence lesser
mtotal and pumping power will be
required, which would reduce the
operating cost of the system.
Result, Discussion and Costing
Based on the Thermal Analysis and Design procedure for IIRCS, developed above, attempt was made to design an IIRCS
using specifications of pipes and pumps available in the market. For RPS, ½” dia. HDPE pipe was chosen, which has 20mm
outer diameter and 2.8mm maximum thickness for 10kg/cm2 rating. For BPHE, 10mm NB, Heavy IS 1239 pipe was
selected, which has 16.7mm outer diameter and 2.9mm thickness.
Applying the procedure discussed in the preceding sections, it was found that when value of v w = 0.9m/s, mtotal = 2kg/s and
total head required for pumping is about 8.8m. The inlet and outlet header appropriate for these conditions would be – DN
63, PN 6 HDPE pipe – i.e., 63mm outer diameter HDPE pipe for 6 kg/cm2 rating. For these requirements, a centrifugal
mono-block pump (high discharge, single phase) with following specifications can be chosen, which is available in the
market – Total Head : 9m, Discharge : 120 lpm, Delivery pipe : 25mm (1”), Power : 0.75 kW (1 HP).
The estimated Installation Cost IIRCS is Rs.100000/- (Rs.45000/- : Material + Labour + Installation Cost, Rs.25000/- : Cost
of Intangible Assets). A 3 TR Split A.C. Unit, required for the same operating conditions, costs Rs.60000/-. Table 5 shows
the cost comparison of the two systems.
Table 5 – Pay-back Period for Integrated Inbuilt Roof Cooling System
S. No.
1.
2.
3.
4.
5.
6.
Comparison Factor
Power Input.
Capital Cost.
Hours of operation.
Units / day.
Units / month.
Power Cost / month.
(Considering Rs.6.00
per
unit
for
residential building.)
Integrated Inbuilt Roof Cooling
System (IIRCS)
750 W
Rs.100000/6 hours operation / day for 6
months / year (total 1080 hours).
3.0 TR Split A.C. Unit
3900 W
Rs.60000/At least 9 hours operation / day for 3
months and 6 hours operation / day
for 3 months (total 1350 hours).
(750 x 6) / 1000 = 4.5 kWh
(3900 x 6) / 1000 = 23.4 kWh
135 units.
702 units.
Rs.688.50 (say, Rs.689/-)
Rs.3580/Saving in cost of power / month = Rs.2891/Saving in cost of power / year = Rs.2891/- x 6 = Rs.17346/- per year. After 6
years, saving in cost of power = 6 x Rs.17346/- = Rs.104076/-
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The operation of IIRCS is assumed to be 6 hours / day for 6 months / year, i.e. total 1080 hours. Here, steady state
conditions are assumed, whereas in practice transient conditions prevail. When the inlet and outlet temperature of the fluid
become same after certain duration of operation, the system can be switched off till the temperature of the ceiling calls for
restarting of cooling. A simple auto-control system can be employed for this.
Table 6 shows the prospects of various types of ETHE / BPHE based space conditioning systems [5].
Table 6 – Prospects of various types of ETHE /BPHE based space conditioning systems [5].
Criteria for
Comparison
Heat Pumps [7]
Pond or Lake Loop Systems [7,9]
More complex in construction, since
they work on the principle of Vapour
Compression Refrigeration System
and hence they have Compressor,
Expansion Device and Evaporator.
Also, these are double circuit, closed
loop systems and they require
refrigerant for their operation.
Integrated Inbuilt Roof
Cooling System [2, 3, 4,
5, 8]
Simple construction.
Simplicity of
construction.
Earth-Air Heat
Exchanger (EAHE)
System [6]
Simple
construction.
Ease in Installation.
Easy to install.
Comparatively, more difficult to
install.
More complex in construction,
since they work on the principle of
Vapour Compression Refrigeration
System and hence they have
Compressor, Expansion Device
and Evaporator. Also, these are
double circuit, closed loop systems
and they require refrigerant for their
operation.
Comparatively, more difficult to
install.
Capital Cost.
Less than or almost
equal to that of
Convention Space
Conditioning
Systems.
Much less
maintenance cost
compared to
conventional
systems.
Less compared to
conventional
systems.
Higher capital cost.
Higher capital cost.
Less than or almost
equal to that of
Convention Space
Conditioning Systems.
Maintenance cost similar to those of
conventional systems, since
components like compressor are
there and refrigerant is also
required.
Less compared to conventional
systems.
Maintenance cost similar to those
of conventional systems, since
components like compressor are
there and refrigerant is also
required.
Less compared to conventional
systems.
Much less maintenance
cost compared to
conventional systems.
No – refrigerant used.
No – refrigerant used.
Maintenance Cost.
Operating Cost.
Are they
Environment
Friendly ?
Yes.
Easy to install, but have
to be installed in newly
constructed buildings
only, not in existing
ones.
Much less compared to
those of conventional
systems, lesser than
EAHE, Heat Pumps and
Pond or Lake Loop
Systems.
Yes.
References
[1]. Urja Bharati – Solar Architecture : Sustainable Designs for Comfortable Space (April 2003), Ministry of Non-Conventional Energy
Sources, New Delhi.
[2]. Vanita N. Thakkar, “Thermal Design Optimization of Integrated Inbuilt Roof Cooling System”, A thesis submitted in partial
fulfilment of the requirements for the degree of Master of Engineering (Thermal Science) at the M. S. University of Baroda,
Vadodara, 2003.
[3]. Vanita N. Thakkar, “Thermal Design Optimization of Integrated Inbuilt Roof Cooling System”, National Conference on Global
Technologies in Manufacturing and Thermal Sciences (GTMTS-2004), Sethu Institute of Technology, July, 2004, Virudhunagar
(Tamil Nadu), India.
[4]. Vanita N. Thakkar, “Techno-economic Analysis of Integrated In-built Roof Cooling System”, Proceedings of Renewable Energy
Asia – 2008, International conference, IIT, 11-13 December, 2008, New Delhi, p – 1065-1072.
[5]. Vanita N. Thakkar, “Recent Trends In Non-Conventional Space-Conditioning Systems”, International Journal of Engineering
Research & Technology (IJERT), Vol. 2 Issue 3, March – 2013, ISSN: 2278-0181.
[6]. Prof. Girija Sharan and Ratan Jadhav, “Performance of Single Pass earth-Tube Heat Exchanger : An Experimental Study”, Journal
of Agricultural Engineering, Vol. 40, Issue 1, January-March, 1-8.
[7]. Steven P. Rottmayer, “Simulation of Ground Coupled Vertical U-Tube Heat Exchangers”, A thesis submitted in partial fulfillment
of the requirements for the degree of Master of Science (Mechanical Engineering) at the University of Wisconsin-Madison, 1997.
[8]. Vanita N. Thakkar, “Study and Analysis of Non-conventional Space Conditioning Systems installed at Universal Medicap,
Vadodara”, Proceedings of International Conference on Advances in Mechanical Engineering, SVNIT, Surat, 3-5 August, 2009, p
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[9]. John W. Bartok, Feasibility Study of a Geothermal Heating System within a Commercial Greenhouse,
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