Page 229 - Low Temperature Energy Systems with Applications of Renewable Energy

216 Low-Temperature Energy Systems with Applications of Renewable Energy

Table 5.8 Thermodynamic parameters of 2-stage HPU at T c ¼ 95 S. Cooling
capacity ¼ 28 kWt; Thermal power ¼ 34.3 kWt; CM1 ¼ 3.06 kW; CM2 ¼ 3.25 kW;
EC ¼ 0.084 kWt; R123 flow rate in EV, _ m EV ¼ 0.203 kg=s, in C, _ m C ¼ 0.204 kg=s; COP
4.44.
Parameters
3
Points P, MPa T, 8S V,dm /kg h, kJ/kg S, kJ/(kg K) x a _ m i = _ m
1 0.076 27.00 206.26 399.58 1.6831 0.997
2 00 0.144 43.82 113.19 409.74 1.6831 0.997
2 0.144 50.43 116.10 414.64 1.6984 0.997
3 0.144 50.41 116.09 414.63 1.6984 1.000
4 00 0.271 68.41 63.03 425.37 1.6984 1.000
4 0.271 74.97 64.66 430.54 1.7134 1.000
5 00 0.271 58.00 60.37 417.17 1.6740 1.000
5 0.271 58.00 0.73 262.31 1.2064 0.997
6 0.271 58.00 0.73 262.31 1.2064 1.000
7 0.144 37.61 15.21 262.31 1.2089 0.132 0.003
8 0.144 44.61 113.54 410.33 1.6850 0.003
9 0.271 57.61 0.73 261.90 1.2052 0.997
10 0.076 20.00 47.22 261.90 1.2137 0.233 0.997
11 00 0.076 20.00 200.68 394.67 1.6666 0.997
11 0.076 27.00 206.26 399.58 1.6831 0.997
a
x ¼ _ m g _ m, the mass of vapor divided by the total mass of a liquid-vapor mixture.
Exergy loss in the low-pressure level compressor is:

E _ CM1 ¼ _ m EV T env ðs 2 s 1 Þ (5.25)
Dk
Exergy loss in the electric motor of the low-pressure compressor is:

_
E _ CM1 ¼ _ m EV W CM1 ð1 h Þ=h (5.26)
Dk el el
_
where W CM1 is the isentropic work of the low-pressure compressor; h fl is electro-
mechanical efficiency of the compressor.
Exergy loss in the high-pressure level compressor is:

E _ CM2 ¼ _ m C T env ðs 4 s 3 Þ (5.27)
Dk
where _ m C is the R123 mass flow rate at the high pressure level.