*4.2.2 VCC validation*

In this section, the operation of the VCC cycle is enabled. Nasir and Kim [31] are selected for the validation. Some changes in the model are made to have an appropriate comparison against the literature. Indeed, the temperature of the condenser is set to 30°C. **Table 3** includes the validation results along with the COP for cooling. We selected three fluids for validation, which are R245fa, R123, and R134a. **Table 3** shows the margin of error between Ref. [31] and our model. The error results for R245fa, R123, and R134a are, respectively, 0.6, 0.44, and 0.92%. These margins are acceptable to give their low values.


**Table 3.** *Validation results for VCC cycle.* *Performance Analysis of a New Combined Organic Rankine Cycle and Vapor Compression… DOI: http://dx.doi.org/10.5772/intechopen.91871*

## **5. Selection of the working fluid**

The choice of the working fluid for an ORC or VCC cycle is an important criterion to improve the cycle performances. Generally, there are three families of organic fluids.

**Figure 9** shows these three classes on a T-S diagram. The distinction between these different types essentially depends on the slope between the saturation temperature and the isentropic variation (ΔT/Δs). If a negative slope is said, the fluid is wet, such as H2O, NH3, and R134a. For a positive slope, we speak of a dry fluid such as benzene and pentane. In cases where the slope is infinite, it is said that this fluid is isentropic like R600 and R600a.

For the ORC cycle is to have fluid hot admits a weak latent heat in the evaporator, in order to minimize the quantity received by the boiler. Thus, a low latent heat in the condenser minimizes the amount of cold delivered by the VCC cycle. In addition, we are looking for a fluid with a positive slope to avoid vapor having less than 0.95 of steam rate.

We guarantee the elimination of the oxidation effect in the turbine especially that we will make it lower concerning the condensation temperature to 10°C. Based on these criteria and conditions mentioned above, it is necessary to choose a dry or isentropic ORC cycle fluid. We choose the n-hexane; the chemical formula is C6H14. The thermophysical characteristics of this fluid are presented in **Table 4**.

The R600 is selected as a working fluid for the VCC cycle. It is a hydrocarbon of formula C4H10 crude which is found in the gas status under normal conditions of temperature and pressure. The physical characteristics of this fluid are presented in **Table 4**. Furthermore, our choice is toward the use of n-hexane for the ORC cycle. This choice is essentially due to the steam rate which is equal to 1 even when the condensation temperature is lowered to a low degree. This allows us to have a margin of confidence and turbine safety (avoid the effect of oxidation). During our study, we chose the R600 as a working fluid for the VCC cycle. This fluid is characterized by its robustness in the market, so it is used in recent years in several researches. In addition, we find that the environmental damage is minimal.

#### **6. System settings and boundary conditions**

To reassure the efficiency and rentability of the system, it is necessary that we set some parameters and define their limits. For example, the network and

**Figure 9.** *The three classes on a T-S diagram.*

similar working applied fluid. The comparative results are illustrated in **Table 2**. These results show a small deviation of 2.09% concerning the thermal efficiency. It is worthy to notice that certain changes in the developed model are made for an appropriate comparison. Specifically, the condensation temperature was 40°C and

**Fluid T4 Pmin Pmax m1 ηorc** R600 Ref. [30] 48.43 2.85 15.28 17.746 12.58

R600a Ref. [30] 45.33 4.038 19.98 2.423 12.12

R245fa Ref. [30] 50.7 1.801 12.67 33.424 12.52

Present model 47.83 2.89 15.52 17.58 12.43 Error 1.23 1.38 1.54 0.93 1.19

Present model 44.61 4.121 19.79 2.371 11.96 Error 1.58 2.01 0.95 2.14 1.32

Present model 49.64 1.765 12.81 34.101 12.44 Error 2.09 1.99 1.09 1.98 0.63

In this section, the operation of the VCC cycle is enabled. Nasir and Kim [31] are selected for the validation. Some changes in the model are made to have an appropriate comparison against the literature. Indeed, the temperature of the condenser is set to 30°C. **Table 3** includes the validation results along with the COP for cooling. We selected three fluids for validation, which are R245fa, R123, and R134a. **Table 3** shows the margin of error between Ref. [31] and our model. The error results for R245fa, R123, and R134a are, respectively, 0.6, 0.44, and 0.92%. These

**Fluid COPvcc** R245fa Ref. [32] 6.60

R123 Ref. [32] 6.70

R134a Ref. [32] 6.45

Present model 6.56 Error 0.60

Present model 6.67 Error 0.44

Present model 6.51 Error 0.92

the isentropic efficiency at 85%.

*Validation results for ORC cycle.*

margins are acceptable to give their low values.

*4.2.2 VCC validation*

**Table 2.**

*Electrodialysis*

**Table 3.**

**10**

*Validation results for VCC cycle.*


**Table 4.**

*Physical and chemical property of work fluids.*

refrigeration capacity must be always positive. Also, to guarantee the safety of the turbines, it is necessary that the vapors' quantity must be more than 95%.

This variation in flow rates does not depend only on the temperature of the solar collector Th, but it also depends on the temperature of the boiler Tg. For this, we have made surfaces of each flow ratio with two temperatures Th and Tg as shown in **Figure 11**. In addition, it can be noticed that the net quantity of the hot water is delivered

*Performance Analysis of a New Combined Organic Rankine Cycle and Vapor Compression…*

*The evolution of different throughput ratios as a function of Th.*

*DOI: http://dx.doi.org/10.5772/intechopen.91871*

*Surfaces of flow reports as a function of each two temperatures Th and Tg.*

**Figure 12** illustrates the evolution of different mass flow rates as a function of the heat delivered Qb by the boiler. The four flows are varied proportionally with Qb. It is

by the system.

**Figure 11.**

**13**

**Figure 10.**

The boundary conditions are shown in **Table 5**.

#### **7. Results analysis and discussion**

The main purpose of this study is to analyze the performance of a new system that combines the steam compression cycle and the Rankine cycle for tri-generation (electricity, cold, hot).

In the previous section, we presented the different designs of the system. This system has an energy autonomy. It needs only the solar temperature "Th." For that reason, we will focus our work on the impact of solar temperature.

First of all, we started with the mass flow analysis of each circuit in order to have the mass potential of our mini power plant.

**Figure 10** resumes the evaluation of the different values of the flow rate for each circuit. The different ratios of the mass flow rates are R1, R2, R3, and R4. The shape of different curves is of positive exponential form. It can be seen that the variation between the four curves is constant in function of Th. The three ratios R1, R3, and R4 represent small variations of the ratios of the flow rates as a function of Th between them. Consequently, the geometries of different constituent bodies are coherent in terms of dimensions. In contrast, the ratio R2 is a large margin of variation compared to the other ratios.


**Table 5.** *Boundary conditions.* *Performance Analysis of a New Combined Organic Rankine Cycle and Vapor Compression… DOI: http://dx.doi.org/10.5772/intechopen.91871*

#### **Figure 10.**

refrigeration capacity must be always positive. Also, to guarantee the safety of the

**Fluid Critical temperature (°C) Critical pressure (bar) MW (kg/kmol)** Ammonia 132.3 113.3 17.03 R600a 134.7 36.4 58.12 R134a 101 40.59 102 R500 105.5 44.55 99.31 R236fa 124.9 32 152 Propane 96.68 42.47 44.1 R245fa 154 36.51 134 Acetone 235 47 58.08 n-Hexane 234.7 30.58 86.17 R600 152 37.96 58.12 R123 183.7 36.68 152.9

The main purpose of this study is to analyze the performance of a new system that combines the steam compression cycle and the Rankine cycle for tri-generation

In the previous section, we presented the different designs of the system. This system has an energy autonomy. It needs only the solar temperature "Th." For that

First of all, we started with the mass flow analysis of each circuit in order to have

**Figure 10** resumes the evaluation of the different values of the flow rate for each circuit. The different ratios of the mass flow rates are R1, R2, R3, and R4. The shape of different curves is of positive exponential form. It can be seen that the variation between the four curves is constant in function of Th. The three ratios R1, R3, and R4 represent small variations of the ratios of the flow rates as a function of Th between them. Consequently, the geometries of different constituent bodies are coherent in terms of dimensions. In contrast, the ratio R2 is a large margin of variation com-

Wnet >0 Qevnet >0 X4 >0.95 Tairin 30 Tairout 18 T6 30

turbines, it is necessary that the vapors' quantity must be more than 95%.

reason, we will focus our work on the impact of solar temperature.

The boundary conditions are shown in **Table 5**.

**7. Results analysis and discussion**

*Physical and chemical property of work fluids.*

the mass potential of our mini power plant.

(electricity, cold, hot).

**Table 4.**

*Electrodialysis*

pared to the other ratios.

**Table 5.**

**12**

*Boundary conditions.*

*The evolution of different throughput ratios as a function of Th.*

This variation in flow rates does not depend only on the temperature of the solar collector Th, but it also depends on the temperature of the boiler Tg. For this, we have made surfaces of each flow ratio with two temperatures Th and Tg as shown in **Figure 11**.

In addition, it can be noticed that the net quantity of the hot water is delivered by the system.

**Figure 12** illustrates the evolution of different mass flow rates as a function of the heat delivered Qb by the boiler. The four flows are varied proportionally with Qb. It is

**Figure 11.** *Surfaces of flow reports as a function of each two temperatures Th and Tg.*

#### **Figure 12.**

*The evolution of flows according to high-temperature heat source.*

noted that the mass flow has a large positive slope with respect to the other mass flow rates. This allows us to interpret that the geometry of the ORC cycle is very important in relation to the different cycles. Also, this cycle promotes significant power.

It is constant that the lowest mass flow rate corresponds to the mass flow rate that does not exceed 0.18 kg/s, which means that the desalinated water is installed at a low power.

In energy potential term provided by our installation, **Figures 13** and **14** indicate the net work and the amount of cold produced as a function of the hot source Qb. It is observed that the two quantities Wnet and Qev are proportional to Qb. It is possible to obtain a net work of maximum value equal to 14 kW and a maximum amount of cold equal to 75 kW.

**Figure 15** shows the evolution of the ORC thermal efficiency as a function of the generator temperature Tg and the vaporization temperature of the cold Tev.

It is observed that the ORC efficiency is proportional to Tg and inversely proportional to Tev; this is justified by the first principle of thermodynamics. A better

*Performance Analysis of a New Combined Organic Rankine Cycle and Vapor Compression…*

The investment costs can be estimated from specialized works [30, 32–36] where they are generally presented in the form of charts or tables. Often these abacuses represent the cost taking into account the influence of parameters such as pressure, temperature, material or manufacturing, assembly, transport, etc.

We have undertaken to gather technical and economic data of the components used in the VCC and ORC cycles (compressors, condensers, evaporators) in order to

efficiency noted is 0.21 for Tev = 10°C and Tg = 95°C.

*Variation of ORC efficiency as a function of Tg and Tev temperature.*

**Figure 14.**

**Figure 15.**

**15**

*Net work variation and cooling capacity according to Q b.*

*DOI: http://dx.doi.org/10.5772/intechopen.91871*

**7.1 Technical-economic analysis and investment costs**

**Figure 13.** *The evolution of flows m4 according to high-temperature heat source.*

*Performance Analysis of a New Combined Organic Rankine Cycle and Vapor Compression… DOI: http://dx.doi.org/10.5772/intechopen.91871*

**Figure 14.** *Net work variation and cooling capacity according to Q b.*

**Figure 15.** *Variation of ORC efficiency as a function of Tg and Tev temperature.*

It is observed that the ORC efficiency is proportional to Tg and inversely proportional to Tev; this is justified by the first principle of thermodynamics. A better efficiency noted is 0.21 for Tev = 10°C and Tg = 95°C.

#### **7.1 Technical-economic analysis and investment costs**

The investment costs can be estimated from specialized works [30, 32–36] where they are generally presented in the form of charts or tables. Often these abacuses represent the cost taking into account the influence of parameters such as pressure, temperature, material or manufacturing, assembly, transport, etc.

We have undertaken to gather technical and economic data of the components used in the VCC and ORC cycles (compressors, condensers, evaporators) in order to

noted that the mass flow has a large positive slope with respect to the other mass flow rates. This allows us to interpret that the geometry of the ORC cycle is very important

It is constant that the lowest mass flow rate corresponds to the mass flow rate that does not exceed 0.18 kg/s, which means that the desalinated water is installed

In energy potential term provided by our installation, **Figures 13** and **14** indicate the net work and the amount of cold produced as a function of the hot source Qb. It is observed that the two quantities Wnet and Qev are proportional to Qb. It is possible to obtain a net work of maximum value equal to 14 kW and a maximum amount of

**Figure 15** shows the evolution of the ORC thermal efficiency as a function of the

in relation to the different cycles. Also, this cycle promotes significant power.

*The evolution of flows according to high-temperature heat source.*

*The evolution of flows m4 according to high-temperature heat source.*

generator temperature Tg and the vaporization temperature of the cold Tev.

at a low power.

**Figure 12.**

*Electrodialysis*

cold equal to 75 kW.

**Figure 13.**

**14**

develop technical-economic and then exergo-economic con-elations. This task is not easy since often the data is discrete and the interpolations or extrapolations are not conclusive due to the nonlinearity of the cost according to the parameters used by the manufacturer.

with

**8. Conclusion**

3500 < QCD < 20,000 [W]

*DOI: http://dx.doi.org/10.5772/intechopen.91871*

/h]

The energy performance of power and refrigeration cogeneration and trigeneration through an organic Rankine cycle (ORC) with a vapor compression cycle

*Performance Analysis of a New Combined Organic Rankine Cycle and Vapor Compression…*

temperature energy source. Two cases of refrigeration and cogeneration are analyzed, including cases of cogeneration (10, 10°C) and congelation (0, 17°C). The effects of the system parameters include the condensation and vaporization

temperatures for ORC and VCC, and the efficiency E on performance such as thermal efficiency, specific refrigeration, and net work output and global system

• The results show that operating parameters have a significant effect on performance. This effect differs from one use case to another (positive or negative refrigeration) and according to the installed configuration (cycles A,

• The three configurations developed which were based on the integration of recovery exchangers noted improvements in overall performance. These improvements also differ from one cycle to another, which makes it possible to

• The results show that for cogeneration with negative cold, among the three configurations that we have developed, cycle B is preferable in which it has a

say that the spot of integration of the exchangers is an effect on the

COPvcc coefficient of performance for the vapor compression cycle

COPs coefficient of performance for the overall system

Cicp investment cost of the compressor CiEV investment cost of the evaporator Cyl piston compressor displacement CiCD investment cost of the condenser

+ H2. H1 cycle with exchangers 1 and 2

DCD heat transfer fluid flow rate at condenser DEV heat transfer fluid flow rate at evaporator

According to the analysis and the investigation carried out during this study, the

(VCC) by a new combination systematic is examined. We can use a low-

0.6 < DCD < 2 [m3

performance are investigated.

B, and C).

performances.

**Nomenclature**

H1 exchanger 1 H2 exchanger 2 H3 exchanger 3

**17**

better energy performance.

main interpretations retained are:
