OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
Ẁ comp,act = ( Ẁ comp / Isentropic ŋ ) (24)
4. THERMAL ANALYSIS OF GSHP SYSTEM FOR A CASE STUDY
The thermodynamic analysis of GSHP system for district heating was investigated in terms of both energy
analyses, which aim at better, identifies the COP of GSHP System. Expression for this analysis was derived
using mass, energy balance equation discussed earlier in the section.
Referring figure 3, it can be observed that the GSHP mainly consist of three separate Circuits
i. The ground coupling circuit ( Brine Circuit ) With a nominal Diameter U- bend ground heat
exchanger,
ii. The refrigerant Circuit
iii. The Fan Coil Circuit ( Water Circuit )
Here we were considering brine water as simple water. The Refrigerant Circuit was built of closed – loop copper
tubing. The Working fluid is R- 22.
The energy performance of a GSHP system can be influenced by three primary factors
i. The heat Pump Machine
ii. The Circulating pump or ground water heat pump
iii. The ground temperature
For evaluating the performance of a GSHP system, the temperature and pressure at the inlet and outlet of a
various components of a GSHP system have to be given or assumed. We are interested to know the effect of
Indian condition on the performance of GSHP system. For this purpose we have to take average temperature of
India during winter. Here we are taking ambient temperature 11˚ C. Changing ground inlet and outlet
temperature according to our condition s for various refrigerants such as R-22 and R134 a, for same heating load
of 5 KW. We are interested to know the comparison in COP for both. Here we are assuming same pressure and
temperature as input for the entire refrigerant. With the help of psychometric Properties chart we get other
required values such as enthalpy and entropy [12]. Now we make table of result for refrigerants one by one then
we compare their result by comparing their COP which include in section of result and discussion. The Soil
temperature is assumed as 20˚C according to our condition for the entire refrigerant. The word brine water is
only used here in actual we are taking the properties of water for making our calculation. The soil temperature
measured in Agra about 20 meter below is comes out to , T soil =20˚C and heat pump Capacity is= 5KW. Overall
efficiency of compressor is about 80%
From equation Q sh =Q cond = r (h 2 -h 3 ),Mass flow rate of refrigerant is comes out to be, r = 0.0253 kg/sec
From the equation Q fc = w C pw (T 5 -T 6 ),we get mass flow rate of water in fan coil unit, w = 0.833 kg/sec where
C pw taken as 4.18 kj/kgk
From the equation Q gh = bw C p.bw (T 8 -T 7 ), Where Q gh = Q evap = r (h 1 -h 4 ), bw = 0.4242 kg/sec
Table 1 Property data for different components of GSHP (R22)
S. No Description Fluid Temp T
˚C
Pressure
P (bar)
Specific Enthalpy
h (kj/kg )
Specific Entropy
s (kj/kgk )
1 - Refrigerant 11 1.013 388.609 1.825
2 - Water 11 1.013 46.31 0.1658
3 - Brine Water 11 1.013 46.31 0.1658
4 Compressor Inlet Refrigerant -2 4.6 404.626 1.75475
5 Compressor Outlet Refrigerant 52 20.32 447.98 1.68
6 Condenser Outlet Refrigerant 40 15.335 249.686 1.1666
7 Evaporator Inlet Refrigerant -5 4.21 194.176 0.9787
8 Fan Coil Unit Inlet Water 50 2.4 211.39 0.7027
70