**8.2 Procedures for vapor compression refrigeration system analysis**

The system has some essential components through which the thermodynamic properties were measured using various mechanical devices on the vapor compression refrigeration system. These components include a single hermetic compressor, evaporator, standard parallel tube condenser, and capillary tube, as shown in **Figure 8**.


**Figure 8.** *Prototype of the vapor compression system.*

*Impact of Working Fluids and Performance of Isobutane in the Refrigeration System DOI: http://dx.doi.org/10.5772/intechopen.99121*


### **8.3 The basic equation for standard vapor compression system**

The following expression explains the relationship between the heat input and output of a refrigeration system. The availability of a pure substance can be defined by Eqs. (1)–(6) [25, 40, 47], assuming there is an insignificant change in kinetic and potential energy across the four essential components [30].

Heat absorbed in the evaporator

$$Q\_{\varepsilon} = \dot{m}(he\_1 - he\_4) \text{ in kW} \tag{1}$$

Where,

*Qe* = heat of evaporator. *he*<sup>1</sup> = specific enthalpy of vapor existing evaporator in kJ/kg. *he*<sup>4</sup> = specific enthalpy of a cooled refrigerant entering evaporator in kJ/kg. *m*\_ = refrigerant mass flow rate in kg/s. Compressor work

$$\mathcal{W}\_c = \dot{m}(hc\_2 - hc\_1) \text{ in kW} \tag{2}$$

Where,

*Wc* = compression work input.

*hc*<sup>2</sup> = specific enthalpy of vapor exiting compressor in kJ/kg. *hc*<sup>1</sup> = specific enthalpy of vapor entering compressor in kJ/kg.

*m*\_ = refrigerant mass flow rate in kg/s.

Coefficient of performance

$$\text{COP} = \frac{\dot{m}(hc\_1 - hc\_4)}{\dot{m}(hc\_2 - hc\_1)}\tag{3}$$

Where,

*COP* = coefficient of performance.

*Qe* = heat of evaporator in kJ/kg.

*Wc* = Compressor work done in kJ/kg.

*m*\_ = mass flow rate of the refrigerant in kg/s.

Refrigerating effect

$$R.E = \text{COP} \cdot \text{W}\_c \tag{4}$$

Where, *R:E* = refrigerating effect. *COP* = coefficient of performance. *Wc* = compressor work done on the working fluid. Heat rejected by the condenser

$$hmod = \dot{m}(hc\_2 - hc\_3) \text{ in kW} \tag{5}$$

Where,

*hcond* = heat of condenser.

*hc*<sup>2</sup> = specific enthalpy of vapor entering condenser in kJ/kg.

*hc*<sup>3</sup> = specific enthalpy of subcooled refrigerant exiting condenser in kJ/kg. Refrigerant mass flow rate.

The refrigerant mass flow rate is defined as the ratio of the refrigerating effect to the enthalpy change in the evaporator.

$$\text{Refrigerant Mass flow rate } (\dot{m}) = \frac{cooling \ load}{he\_1 - he\_4} \text{ in kg/s} \tag{6}$$

### **9. Result and discussions**

**Figures 6**, **9**, and **10** explain the thermodynamic effect that occurs in the refrigeration system. **Figure 9** shows the system's evaporating temperature (ET) when working with R600a and R134a refrigerants. The system attained its ET, the minimum operating temperature of �26°C while working with R600a in 3 hours compared to when the system worked with R134a and attained ET of �22°C in 5 hours.

**Figure 6** displayed the hermetic compressor's power when the system worked with R600a and R134a refrigerant. It was clear that the system's energy consumption rate using R600a was 23.3% lower than when the system worked with R134a. The result obtained means the refrigeration system performed excellently with R600a refrigerant at ET of �26°C.

**Figure 10** shows the domestic refrigeration system's coefficient of performance when working with R600a and R134a refrigerants. The result indicates that the system has a better working operation when working with R600a refrigerant. That is, the COP increases by 27.1% compared to when it worked with R134a.

**Figure 9.** *Variation ET of R600a and R134a with the time taken.*

*Impact of Working Fluids and Performance of Isobutane in the Refrigeration System DOI: http://dx.doi.org/10.5772/intechopen.99121*

**Figure 10.** *Coefficient of performance with time.*
