buletinul institutului politehnic din iaşi - Universitatea Tehnică ...

Bul. Inst. Polit. Iaşi, t. LVIII (LXII), f. 4, 2012 299
In this section, the method and step calculation for eco-efficiency of
single stage refrigeration system will be described. Fig. 1 shows the schematic
representation of the single stage refrigeration system which must be retrofitted
from R404A to R717. The R404A refrigerant from the discharge compressor
port goes to the condenser (where appear the condensation process), then from
the condenser outlet it goes into liquid receiver. From the liquid receiver the
refrigerant enter in evaporator 1 and 2 (where appear evaporation process) and
after the evaporator the refrigerant goes to suction port of the compressor.
First the working conditions are described; secondly the theoretical ecoefficiency
parameters (presented in the introduction) and thirdly the results of
the theoretical study are shown.
The working conditions are given in Table 1. The refrigeration system
works 8 hours/day (nhours) and 261 days/year (ndays). The life cycle of the
refrigeration system is 15 years (nyears). The refrigerant charge (m) is: R404A –
14kg, R717 – 6.45 kg and R507A – 14.11 kg. The requirement electrical power
(Pe) is shown in Table 1. The carbon dioxide emission (β) is 0,6kg/kWh. The
recovery factor (αrec) is 75%. The refrigerant leak (msc) is 8%.
The electrical power values were calculated and established by each
refrigeration system, depending on properties and evaporation temperature
(Zabet, 2011).
Table 1
Working conditions
Refrigerant Φ0 (kW)
M
(kg)
Tc (K)
TSH (K)
TSUB (K)
T0 (K)
263.2 273.2
Pe (kW)
278.2
R404A 12.3 14 3.70 5.25 5.47
R717 10 6.45 308.2 10 3 3.55 4.00 3.85
R507A 10 14.11
3.80 3.94 4.07
where: Φ0 is refrigerant capacity, T0 evaporation temperature; TC condensing
temperature, TSH superheating temperature; TSUB subcooling.