Influence Of Internal Heat Exchanger Research Articles

Internal Heat Exchanger Influence in Operational Cost and Environmental Impact of an Experimental Installation Using Low GWP Refrigerant for HVAC Conditions

The use of an internal heat exchanger in vapor compression refrigeration systems of one stage is a common practice because it helps to increase the cooling capacity in the evaporator. Furthermore, the use of refrigerants with low global warming potential is becoming more frequent due to environmental regulations worldwide. Thus, this paper presents an evaluation of the improvement produced by the inclusion of an internal heat exchanger cycle (IHXC) in an experimental installation from the viewpoint of exergy, economic and environmental through to exergy, exergoeconomics, and Specific Life Cycle Climate Performance (SLCCP) studies. The tests were conducted using R1234ze(E) as a replacement alternative to R134a in three evaporating temperature conditions: 4 °C, 9 °C, and 14 °C. Comparisons were made considering R134a in BRC mode versus R1234ze(E) in BRC and IHXC modes. Results show that a lower environmental impact is produced by an evaporating temperature of 14 °C with a reduction in SLCCP of 13.3% using IHXC and R1234ze(E). Moreover, the highest increase in exergy efficiency was observed for an evaporating temperature of 4 °C, with this increase being 9%, while the lowest increase in the total cost rate was observed for the same evaporating temperature, being 12.3% and 21.2% for BRC and IHXC modes using R1234ze(E), respectively.

Experimental study of influence of internal heat exchanger in a chest freezer using r-513a as replacement of r-134a

• Use of IHX in a chest-freezer reduce the time to reach the stability temperature in the indoor cabin of equipment. • The energy consumption was reduced in 8% using R-513A in comparison with R-134a. • The optimal refrigerant mass charge was reduced in 6.25% when the R-513A were used in comparison with R-134a. • The running time ratio for R-513A was lower than R-134a in 11.8%. Internal Heat Exchanger (IHX) in vapor compression refrigeration cycle is an alternative to improve the energy performance in refrigeration systems. In this paper, the influence of IHX on thermal behavior of a chest freezer is evaluated experimentally. For the study, R-513A is used as replacement refrigerant of R-134a. Results indicate that the optimal refrigerant mass is less for the R-513A than R-134a under the same operating conditions. When R-513A is used as refrigerant, a reduction of 6.25% in refrigerant mass in comparison with the R-134a refrigerant is achieved. Also, it is found that the stability time in the indoor compartment is reduced by 2 and 4 h when the R-513A was used in comparison with the R-134a with and without IHX, respectively. Finally, energy consumption for R-134a is 8% higher for 24-h energy consumption test, in comparison with R-513A.

Numerical study on the influence of internal heat exchanger in transcritical CO2 heat pumps under optimal pressure conditions

This paper presents a numerical study on the influence of internal heat exchanger (IHX) exchanging surface in the performance of a transcritical CO2 heat pump water heater at different operating conditions. Five different IHX geometries and four different evaporation temperatures have been studied with water temperature ranging from 10 °C to 60 °C at the gas cooler inlet. The results show a strong influence of IHX characteristics on system’s performance.

The Influence of Internal Heat Exchanger on the Performance of Transcritical CO2 Water Source Heat Pump Water Heater

The characteristics of the transcritical CO2 heat pump water heater (HPWH) system are; a lower inlet hot water temperature (Ti-hw) (sometimes this is lower than the water source temperature), and an outlet gas cooler temperature (To-gc) which is affected by the Ti-hw and often lower than the critical temperature. In order to study the effects of the internal heat exchanger (IHX) on the operational performance of the transcritical CO2 HPWH when To-gc is low, a transcritical CO2 water source HPWH experiment platform is established to conduct experimental research and comparative analysis on the operational performance of the transcritical CO2 water source HPWH, with or without IHX. It is found that, if only the coefficient of performance (COP) and heating at the optimal exhaust pressure of the transcritical CO2 water source HPWH were considered, COP and the heating of the non-IHX system would be slightly higher than those of the IHX system at the lower hot water flow and water source temperature, and this increase was not obvious. At the higher hot water flow rate and water source temperature, COP and the heating of the non-IHX system were also higher than those of the IHX system, and the increase was obvious. The experiment results showed that, near the optimal exhaust pressure, the variation range of COP and heating of the IHX system is relatively small, and the system has a relatively high stability.

Experimental investigation on the influence of internal heat exchanger in a transcritical CO2 heat pump water heater

In this paper, a transcritical CO2 heat pump water heater prototype was experimentally investigated to research the influence of internal heat exchanger (IHX). In addition, the exergy analysis was carried out based on the experimental data. The results showed that the optimal discharge pressure reduced with the application of IHX, and this reduction could be amplified by the decrease of the ambient temperature, the increase of the water inlet temperature and the increase of the water outlet temperature. From the energy point of view, under the optimal discharge pressure, the coefficient of performance (COP) increased by up to 6.65% and the total power consumption decreased by up to 6.22% via using IHX. Then the influence of IHX on the heat pump cycle was discussed. The results of the exergy analysis showed that the exergy destruction of compressor, gas cooler and evaporator increased, and the exergy destruction of expansion valve decreased with the application of IHX. Furthermore, the product exergy and the total exergy destruction increased, and the exergy efficiency of system decreased in all working conditions. In conclusion, the application of IHX enhanced the energy performance and impaired the exergy efficiency in this research.

The influence of internal heat exchanger on energy efficiency and environmental effects of the Heat Pump using Low-GWP Refrigerants as substitutes

This paper presents an experimental analysis of the influence of heat exchanger on the performance of a heat pump system using Low-GWP refrigerants as replacements for R22. In this work, we compare the energy performance of a monitored heat pump system using NC01(composed of R32, R1234ze(E), and R134a at a mass percentage of 50%:17%:33%), R32 and R1234ze(E) with and without the presence of an internal heat exchanger. From the experimental results, COP reductions of R1234ze(E), NC01 and R32 was 12%, 4% and 1.9% respectively, although the presence of an IHX can help to lessen these reductions between 2 and 6%. The results indicated lower TEWI amounts as a result of using NC01 as an alternative to R22 with the presence of IHT (internal heat exchanger).

Experimental analysis of the internal heat exchanger influence on a vapour compression system performance working with R1234yf as a drop-in replacement for R134a

This paper presents an experimental analysis of the influence of an internal heat exchanger on the performance of a vapour compression system using R1234yf as a drop-in replacement for R134a. In this work, we compare the energy performance of a monitored vapour compression system using both refrigerants, R134a and R1234yf, with and without the presence of an internal heat exchanger under a wide range of working conditions. A set of experimental tests are carried out varying the condensing temperature, the evaporating temperature and the internal heat exchanger use. From the experimental results, reductions in cooling capacity and COP between 6 and 13% have been observed when R134a is replaced by the drop-in fluid R1234yf, although the presence of an IHX can help to lessen these reductions between 2 and 6%. Finally, the experimental results obtained agree with the theoretical evaluations developed neglecting the pressure drops.

Experimental Study of an Internal Heat Exchanger Influence on R134a Automobile Air Conditioning System

Liquid-suction or internal heat exchanger (IHX) is installed in vapor compression refrigeration systems to exchange energy between cool low-pressure gas and warm high-pressure liquid refrigerant. The aim of this research is to experimentally evaluate the effect of IHX adaptation in an automotive air conditioning system focusing on evaporator working conditions. In this new design of IHX, the high-pressure liquid passes through the central channel and the low-pressure vapor flows in several parallel channels in the opposite direction. The experimental set-up has been made up of original components of the air conditioning system of a medium sedan car, specially designed and built to analyze vehicle A/C equipments under real work conditions. The results show that low pressure drop will be imposed on the cycle using this type of IHX. Also, they confirm considerable decrease of compressor power consumption; it is intensified at higher evaporator air flow. A significant improvement of the coefficient of performance will be achieved with IHX too. The influence of operating conditions has been also discussed in this paper.

Numerical simulation and experimental validation of internal heat exchanger influence on CO 2 trans-critical cycle performance

The present paper is a numerical and experimental comparative study of the whole vapour compression refrigerating cycle in general, and reciprocating compressors in particular, with the aim of showing the possibilities that CO 2 offers for commercial refrigeration, considering a single-stage trans-critical cycle using semi-hermetic reciprocating compressors under small cooling capacity systems. The present work is focussed on the influence of using an internal heat exchanger (IHX) in order to improve the cycle performance under real working conditions. In order to validate the numerical results, an experimental unit specially designed and built to analyze trans-critical refrigerating equipments considering IHX has been built. Both numerical results and experimental data show reasonable good agreement, while the comparative global values conclude the improvement of cooling capacity and COP when IHX is considered in the CO 2 trans-critical cycle.

Experimental evaluation of internal heat exchanger influence on R-22 window air conditioner retrofitted with R-407C

The performance of one ton of refrigeration window air conditioner working with R-22 and retrofitted with eco friendly alternative refrigerant R-407C is experimentally investigated An internal heat exchanger is also added to the same air conditioner to provide liquid overfeeding operation. When retrofitting the R-22 system with R-407C, the coefficient of performance is found to drop by 7.28%, however when internal heat exchanger is included the performance is improved. It is observed that the inclusion of internal heat exchanger has increased the coefficient of performance by 5.86% when running on R-22 and 6.18% when running on R-407C, under the given conditions.

05/02745 Experimental evaluation of the internal heat exchanger influence on a vapour compression plant energy efficiency working with R22, R134a and R407C

This paper presents a detailed exergy analysis of an actual vapour compression refrigeration (VCR) cycle. A computational model has been developed for computing coefficient of performance (COP), exergy destruction, exergetic efficiency and efficiency defects for R502, R404A and R507A. The present investigation has been done for evaporator and condenser temperatures in the range of −50 °C to 0 °C and 40 °C to 55 °C, respectively. The results indicate that R507A is a better substitute to R502 than R404A. The efficiency defect in condenser is highest, and lowest in liquid vapour heat exchanger for the refrigerants considered.

Experimental evaluation of the internal heat exchanger influence on a vapour compression plant energy efficiency working with R22, R134a and R407C

Internal or liquid-suction heat exchangers are used in many refrigeration and air conditioning systems based on the vapour compression cycle, with the basic objective of assuring the entrance of refrigerant in liquid phase to the expansion device. This purpose is achieved by exchanging energy between the cool gaseous refrigerant leaving the evaporator and warm liquid refrigerant exiting the condenser. These devices can have positive or negative influences on the plant overall energy efficiency, depending on the working fluid and the operating conditions. In this paper the experimental results obtained from a refrigeration test facility with and without the presence of an internal heat exchanger, using R22, R134a and R407C as working fluids, are presented and analyzed, including the impact of pressure drops and variations of refrigerant mass flow rate. A comparison between experimental and theoretical results is also enclosed.