Increase In Condenser Temperature Research Articles

Thermoeconomic performance analysis of different configurations of a combined ORC-VCR system using zeotropic mixtures

From the perspective of environmental protection, the application of new environment-friendly working fluids provides more feasibility for sustainable development. In addition, the improvement of system configuration increases the possibility of improving system performance. In this paper, the thermodynamic and economic performance model of the organic Rankine cycle (ORC)-vapor compression refrigeration (VCR) combined system is established. Four system configurations and 12 zeotropic mixtures on the system performance are researched and compared. The effect of operating parameters on system performance is studied. The results show that the recuperative-regenerative ORC-VCR (RR-ORC-VCR) system is confirmed as the optimal system configuration. Compared with the basic ORC-VCR (B-ORC-VCR) system, the coefficient of performance (COP) and exergy efficiency are improved by 14.65 % and 10.03 %, respectively. While the total cost increases by 6.85 %. The most suitable working fluid is R245fa/R1234yf (0.55/0.45). Higher glide temperature can be an important criterion in the selection of zeotropic mixtures. When the suction pressure ratio is 0.6, exergy efficiency and total cost are optimal, which are 11.95 % and 1.34 × 105$, respectively. While the highest COP with 0.73 is achieved when the suction pressure ratio is 0.65. With the increase of boiler temperature, the thermodynamic performance of the system increases obviously, but the economic performance decreases. The increase in condenser temperature has a negative impact on the system thermodynamic and economic performance. The growth of evaporator temperature is positively correlated with COP and negatively correlated with exergy efficiency and total cost.

First and Second Law Analysis of Cascade Refrigeration System Using Refrigerant Pair R744-R1234ze(E)

— The performance of a two stage cascade refrigeration system using environment friendly refrigerant pair R744 in low temperature cycle and R1234ze(E) in high temperature cycle has been examined by mathematical simulation in EES ( Engineering Equation Solver). The operating parameters considered in this study are evaporator temperature and condenser temperature. The results shows that with increase in condenser temperature, total exergy loss is increasing and total COP is decreasing. The similar effect has been seen with increase with evaporator temperature but rate of increase of total exergy loss and rate of decrease of total COP with evaporator temperature is low.

Vapour compression system analysis undergoing expansion in an ejector

This paper presents the analysis of a vapour compression system undergoing isentropic expansion in an ejector instead of irreversible isenthalpic expansion in conventional expanding devices i.e. capillary tube, thermostatic expansion valve etc. Comparative energy analysis of the optimized ejector expansion vapour compression system (EEVCS) has been done for commercially used refrigerants R134a, R407C and R410A and it is found that the COP enhancement over standard vapour compression system (VCS) is maximum for R410A (11.49%) followed by R407C (10.16%) and least in R134a (9.261%) at fixed condenser and evaporator temperature of 35°C and 5°C respectively. COP of both the systems decreases with the increase in condenser temperature, however the optimized ejector expansion vapour compression system exhibits less drop in its performance as compared to standard vapour compression system at the same condenser and evaporator temperature. The computational analysis has been carried out in Engineering Equation Solver (EES).

Exergy investigation of a vapor compression system comprising ejector for isentropic expansion

A modified vapor compression refrigeration system using ejector as an expansion device has been studied in this paper. The new system gives higher cooling effect and requires lesser compressor work than typical vapor compression system under similar operating conditions. Exergy analysis has been done to determine the scope of performance improvement in various components of the modified system. Three refrigerants namely R134a, R407C and R410A have been taken for the analysis due to their wide usage in the commercial refrigeration and air conditioning systems. The system is found to have highest 2nd law efficiency of 53.32% with R134a at 35°C condenser temperature and 5°C evaporator temperature. The increase in condenser temperature increases the total irreversibility of the system. The maximum exergy destruction has been observed in condenser for all the refrigerants. The analysis has been carried out in Engineering Equation Solver.

Thermodynamic and transient analysis of the hybrid concentrated photovoltaic panel and vapour compression cycle thermal system for combined heat and power applications

This research conducts a thermodynamic and transient analysis of the hybrid concentrated photovoltaic panel and vapour compression cycle thermal (CPV-VCC/T) system that is designed for combined heat and power purposes. The model includes both the VCC’s thermodynamic model and the evaporator (CPV side) heat exchanger’s convective heat transfer effect. Various commercial refrigerants (R123, R22, R245fa and R134a) are analyzed where their performances are assessed in terms of coefficient of performance (COP) and the CPV’s resulting operating temperature. After the comparative steady state analysis, the CPV-VCC/T system is then tested in a two-day transient simulation involving varying irradiances and hot water demands. Steady state results demonstrate that the COP efficiency relative to Carnot will generally decrease as the condenser temperature increases. Also, although refrigerants R134a and R22 yielded up to 12% higher static COPs than R245fa and R123, the yielded electric energy gain from the two-day transient simulation is different by no more than 1.5%. Positively, the CPV-VCC/T system is found to yield 35% more electric energy than the conventional electric heating system. Although the CPV-VCC/T system yielded 5% less electric energy than direct water cooling, the CPV temperature was successfully maintained at 330 K as opposed to over 380 K.

Thermodynamic analysis and optimization of a solar-powered transcritical CO2 (carbon dioxide) power cycle for reverse osmosis desalination based on the recovery of cryogenic energy of LNG (liquefied natural gas)

A solar-powered transcritical CO2 (carbon dioxide) power cycle for reverse osmosis desalination based on the recovery of cryogenic energy of LNG (liquefied natural gas) is proposed. The system consists of a solar collector subsystem, a transcritical CO2 power cycle subsystem, a LNG subsystem and a RO (reverse osmosis) desalination subsystem. A thermal storage unit is introduced into the system to guarantee continuous and stable operation of the system. A mathematical model is developed to simulate the system based on several assumptions. The effects of several key thermodynamic parameters on the system performance are examined based on the performance criteria, including daily exergy efficiency, daily mechanical work output and daily fresh work output. Parametric optimization is conducted by genetic algorithm to maximize the daily fresh water output. The results show that the CO2 turbine inlet pressure has an optimal value to reach the daily maximum exergy efficiency under the given conditions. The daily exergy efficiency could decrease with an increase in condenser temperature, and increase with an increase in mass flow rate of oil and NG turbine inlet pressure. Through parametric optimization, the system can reach the daily exergy efficiency of 4.90% and provide 2537.33 m3 fresh water per day under the given conditions.

Numerical Study of Ejector as an Expansion Device in Split-Type Air Conditioner

This paper presents a numerical approach for determining the motive nozzle and constant-area of an ejector as an expansion device, based on cooling capacity of the split-type air conditioner using R22 as working fluid. The use of an ejector as an expansion device in split-type air conditioner can enhance the coefficient of performance (COP) system. Typically, the split-type air conditioner may be installed on the geographical area with moderate or high outdoor air temperature using capillary tube. For this reason, the motive nozzle and constant-area diameters of the ejector must be designed according to these conditions. The diameters of the ejector are crucial in improving the COP. The results showed that the motive nozzle diameter is constant (1.14 mm) with variations of the condenser temperature, whereas the constant-area diameter decreases as the condenser temperature increases.

Numerical Study of an Ejector as an Expansion Device in Split-type Air Conditioners for Energy Savings

The present study describes a numerical approach for determining both the motive nozzle and constant-area diameters of an ejector as an expansion device, based on the cooling capacity of a split-type air-conditioner using R290 as refrigerant. Previous studies have shown that replacement of HCFC R22 with HC290 (propane) in the air conditioner can improve the coefficient of performance (COP). The purpose of replacing the capillary tube with an ejector as an expansion device in a split-type air conditioner using HC290 is to further improve the COP. In developing the model, conservation laws of mass, momentum and energy equations were applied to each part of the ejector. The numerical results show that the motive nozzle diameter remains constant (1.03 mm) under varying condenser temperatures, whereas the diameter of the constant-area decreases as the condenser temperature increases. It was also found that improvement of the COP can reach 32.90% at a condenser temperature of 55 °C. From the results mentioned above, it can be concluded that the use of an ejector can further improve the COP of a split-type air conditioner using HC290 as working fluid.

Geometric parameter optimization of ejector-expansion refrigeration cycle with natural refrigerants

Thermodynamic analyses and comparison of ammonia-, propane- and isobutane-based vapour compression refrigeration cycles are presented in this article using constant area mixing ejector as an expansion device. Optimization of ejector geometric parameter based on the maximum cooling COP and performance improvement for different operating conditions is studied. Results show that the optimum geometric parameter increases with increase in evaporator temperature and decrease in condenser temperature, whereas the COP improvement over basic expansion cycle increases with the increase in condenser temperature and decrease in evaporator temperature. Expressions for optimum ejector geometric parameters have been developed, which offer useful guidelines for optimal design and operation. Study shows that the optimum parameters as well as COP improvement using ejector as expansion device are strongly dependent on the refrigerant properties as well as the operating conditions. The optimum geometric parameter is maximum for ammonia, whereas minimum for isobutane. Using ejector as an expansion device, isobutane yields maximum COP improvement of 21.6% followed by propane (17.9%) and ammonia (11.9%) for studies ranges. Copyright © 2009 John Wiley & Sons, Ltd.

Experimental and theoretical investigation of an innovative evaporative condenser for residential refrigerator

In this study, an innovative, evaporative condenser for residential refrigerator was introduced. A vapor compression cycle incorporating the proposed evaporative condenser was tested to evaluate the cycle performance. To allow for evaporative cooling, sheets of cloth were wrapped around condenser to suck the water from a water basin by capillary effect. The thermal properties at the different points of the refrigeration cycle were measured for typical operating conditions. The experimental results showed that the condenser temperature increases 0.45 °C for each degree increase in evaporator temperature when the air velocity is 2.5 m/s, and the ambient condition is 29 °C and the relative humidity is 37.5%. Meanwhile, the condenser temperature increase is 0.88 °C in the case of air velocity 1.1 m/s and ambient conditions of 31 °C and relative humidity of 47.1%. A theoretical model for the evaporative condenser was developed, and validated by experimental results. The theoretical model showed that the evaporative condenser can operate at a condensing temperature of 20 C lower than that of the air-cooled condenser for heat flux of 150 W/m 2, and at air velocity 3 m/s. The effect of the different parameters on the condenser temperature was studied too.

EXPERIMENTAL AND THEORETICAL INVESTIGATION OF AN INNOVATIVE EVAPORATIVE CONDENSER FOR RESIDENTIAL REFRIGERATOR

In this study, an innovative, evaporative condenser for residential refrigerator was introduced. A vapor compression cycle incorporating the proposed evaporative condenser was tested to evaluate the cycle performance. To allow for evaporative cooling, sheets of cloth were wrapped around condenser to suck the water from a water basin by capillary effect .The thermal properties at the different points of the refrigeration cycle were measured for typical operating conditions. UThe experimental results showed that the condenser temperature increases 0.45 o C for each degree increase in evaporator temperature when the air velocity 2.5 m/s, and the ambient conditions is 29 o C and the relative humidity is 37.5 %, Meanwhile, the condenser temperature increase is 0.88 o C in the case of air velocity 1.1 m/s and ambient conditions of 31 o C and relative humidity of 47.1 %. UA theoretical model for the evaporative condenser was developed, and validated by experimental results. The theoretical model showed that the evaporative condenser can operate at a condensing temperature 20 C lower than that of the air cooled condenser for Uan averageU heat flux of 150 W/m2 , and at air velocity 3 m/s. The effect of the different parameters on the condenser temperature was studied too.

Thermodynamic Evaluation of Geothermal Power Generation Systems in Turkey

There is a tremendous potential to improve performance of geothermal applications in Turkey. Exergy analysis is proven to be a powerful tool in performance analysis of geothermal applications. Geothermal energy assisted processes can be improved and optimized dependent upon exergy analysis. In this study, a thermodynamic analysis is presented for optimizing and describing the effective working conditions for geothermal power generation systems (GPGS) in Turkey. For this purpose, an exergy-based approach is performed for simple organic Rankine cycle (ORC). The variations of the parameters that affect the system performance such as working fluid, evaporation temperature, condenser temperature, mass flow rate, and dead state conditions are examined. First and second law efficiencies, total irreversibility, and economical profit based on network output of turbine are calculated for geothermal power generation systems. The results of the analysis show that the first and second law efficiencies decrease with decreasing of evaporation temperature. Similarly, total irreversibility increases while the second law efficiency and economical profit decreases as the condenser temperature increases.