Compressor Discharge Temperature Research Articles

Vapor injected compression with economizing in packaged air conditioning systems for high temperature climate

Operating packaged air conditioning systems at extremely high temperature ambient conditions result in severe performance degradation. In this paper, vapor injection (VI) with economization is proposed to improve system performance. An Environmental Control Unit (ECU) operating with R-407C has been retrofitted with an economized vapor injection (EVI) system and experimentally characterized in side-by-side psychrometric chambers. The performance of the EVI system for superheated and saturated injection conditions were compared to the case of without injection at different operating conditions. The results showed that the EVI system reduced the compressor discharge temperature by up to 5° C, and improved the cooling capacity and COP by up to 12.7% and 3.1%, respectively. The experimental data have been used to develop, tune, and validate a detailed steady-state cycle model. At last, the model has been employed to optimize the economizer geometry in order to maximize the system COP under such extreme weather conditions.

Aero engine compressor cooling by water injection - Part 1: Evaporative compressor model

The need for more fuel-efficient turbofan engines has led to a rise in compressor pressure ratio and turbine inlet temperature respectively. The latter has been possible with advancements in turbine blade technology. Nevertheless, this higher temperature during combustion increases the production of thermal Nitrogen Oxides. Contrary to this high-pressure, high-temperature aero-engine design trend, regulations are pushing towards capping or reducing emissions. Injecting atomised water into a jet engine is an alternative to mitigate Nitrogen Oxides that is applied extensively to stationary gas turbines. The application for jet engines is very limited and dates back to the early Boeing 707 and 747 for thrust augmentation. The focus of this study is to investigate the performance benefits of water injection when applied to 2 and 3-spool compressors, under a wide range of different environmental conditions, and for different injection properties. In this first paper, a thermo-analytical compressor model with water droplet investigations in the Lagrangian frame of reference is explored. The methodology is applied to two different engine architectures, representative of modern turbofan engines. This water injection study focuses on cooling the core and shows that the percent reduction in compressor discharge temperature is promising over a wider range of ambient conditions than expected. The effect of droplet sizes or quantity utilised were seen to be more influential. The 3-spool compressor also appears to benefit more from water injection, mainly due to the higher operating pressures and temperatures found on the Intermediate Pressure Compressor which enables more efficient evaporation, as compared to a booster compressor. Given the design of this compressor, two locations of injections were considered. Reductions in Compressor Discharge Temperature of 60 and 80 K were seen for the 2 and 3-spool engines, for a 2% injection ratio, accompanied by reductions in specific compressor work of 16 and 17%. Part 2 of this study has considered boundary conditions obtained here, to investigate the performance and emissions of complete jet engines.

Aero engine compressor cooling by water injection - Part 2: Performance and emission reductions

Take-off and climb up to 3000 ft are the flight segments in which the aero-engine experiences the highest operating temperatures, which are known to be accompanied by a high production rate of Nitrogen Oxides (NOx). This contaminant has negative health implications on the human population, vegetation and wildlife that is in frequent proximity or exposure. Water injection into the compressor offers the possibility of reducing NOx. Nevertheless, limited studies have focused on the emissions reduction potentials and the wider questions of the influence of engine type and of wide-ranging ambient conditions.This study continues from Part 1 and explores the implications of the studied ambient conditions on the overall respective engine systems and their consequent emission reduction. An in-house gas turbine performance simulation software has been implemented to model and simulate the engine performance. For the emissions estimation, correlations were made from the information provided by the Engine Emissions Data Bank to quantify the reductions in Nitrogen Oxides.The 2 and 3-spool engine models investigated demonstrated significant reductions in compressor discharge and turbine inlet temperatures due to water injection. In this condition, the rotational speeds of the compressors are seen to be reduced to counter the mass flow augmenting effect of water injection and to satisfy the fixed thrust constraint. This along with lower compressor specific work brings about an improvement in the specific fuel consumption (5.3% and 7.8%, respectively) and general performance at low and high ambient temperatures. A higher advantage was seen for the 3-spool engine over the 2-spool as shown. Significant reductions in Nitrogen Oxide emissions of over to 50% are also demonstrated.

Experimental Investigation into the Effect of Oil Injection on the Performance of a Variable Speed Twin-Screw Compressor

In this paper, the effect of oil injection flow rate on the performance of a variable speed twin-screw compressor was investigated experimentally. Comprehensive experiments were conducted at different compressor rotational speeds and oil injection flow rates. As the rotational speed increased from 1000 to 3000 rpm, the compressor volumetric and adiabatic efficiencies increased while the specific power consumption decreased. However, the oil injection flow rate showed different influences on the compressor performance. As the oil injection flow rate increased from 27 to 50 L/min, the adiabatic and volumetric efficiencies increased while the compressor discharge temperature and specific power decreased. Further increases in the oil injection flow rate had little effect on compressor performance at flow rates above 50 L/min. The analysis indicated that the oil injection flow rate was limited by the discharge temperature at low compressor rotational speeds and was a trade-off among two efficiencies and specific power consumption at high rotational speeds.

Theoretical analysis of suitable fluids for high temperature heat pumps up to 125 °C heat delivery

Industrial processes with applications such as pasteurization, drying and distillation have heat demand at a temperature between 100–125 °C. Industries with large amounts of waste heat and cooling demand will benefit from the development of high temperature heat pumps (HTHPs) which can replace conventional heating and waste heat disposal systems. This potentially saves both investment and operational cost of a boiler and a cooling tower with a single more efficient and less complex energy system. At the same time, the environmental footprint is reduced. The working fluids for these high temperature heat pumps using the vapour compression technology are often constrained by their high compressor suction and discharge temperature as well as the safety and environmental impact of the fluids. Within these limits, this paper conducts a theoretical analysis to evaluate available and potential fluids with thermodynamic properties that are applicable for HTHPs. The evaluations show that certain hydrocarbons and halocarbons are the most promising fluid candidates for waste heat upgrade from low temperatures to high temperatures, up to 125 °C.

Energetic and exergetic analysis of a domestic refrigerator system with LPG as a replacement for R134a refrigerant, using POE lubricant and mineral oil based TiO2-, SiO2- and Al2O3-lubricants

This paper experimentally investigated energetic and exergetic performance analysis of a domestic refrigerator using R134a and LPG refrigerants with different lubricants (polyol-ester (POE), mineral oil (MO), and TiO2, SiO2, Al2O3 nanoparticles dispersed in mineral oil).The energetic and exergetic performance analysis of the domestic refrigerator were investigated with test parameters including compressor power consumption, cooling capacity, coefficient of performance (COP), discharge temperature, irreversibility in the components, total irreversibility and second law efficiency. Findings showed that the lowest compressor power consumption and total irreversibility were observed in refrigerator with 40 g charge of LPG/TiO2-MO lubricant (0.2 g/L of TiO2); these values of compressor power consumption and total irreversibility were 15.87% and 31.69%, respectively, lower than for R134a/POE lubricant. In addition, the domestic refrigerator using LPG refrigerant at 40 g charge with TiO2-MO (0.2 g/L TiO2) lubricant, had the highest COP and second law efficiency among the selected nano-lubricants. These values of COP and second law efficiency were 56.32% and 47.06%, respectively, higher than that of R134a/POE. Futhermore, compressor discharge temperature of the domestic refrigerator with 40 g charge of LPG/TiO2-MO lubricant (0.2 g/L of TiO2) was found to be lower than that of R134a/POE. Hence, extended compressor life may be expected with the adoption of TiO2-Mineral oil lubricant. It can be concluded that based on energetic and exergetic performance analysis, the domestic refrigerator using the 40 g charge of LPG/TiO2-MO (0.2 g/L TiO2) performed better than R134a/POE.

Analysis of two-phase injection heat pump using artificial neural network considering APF and LCCP under various weather conditions

The objective of this study is to optimize the performance of a two-phase injection (TPI) heat pump considering annual performance factor (APF) and life cycle climate performance (LCCP). The performances of non-injection (NI), vapor injection (VI), and TPI heat pumps are measured under various outdoor temperatures. Based on the measured data, artificial neural network models for the NI, VI, and TPI heat pumps are developed to predict the performance indexes during cooling and heating seasons. As a result, the TPI heat pump shows higher heating capacity than the NI and VI heat pumps with a lower compressor discharge temperature in cold weather conditions. Therefore, the application of the TPI has a merit on reducing the size of the heat pump due to its lower back-up heater loss and over-capacity penalty. When the objective function maximizes the APF for system optimization in three climate regions, the TPI heat pump shows a 1.4–2.7% higher APF than the NI heat pump, and a 11.1%–18.1% smaller optimum rated heating capacity.

Energy analysis of a domestic refrigerator system with ANN using LPG/TiO2–lubricant as replacement for R134a

This paper experimentally investigated and also modeled using artificial neural networks (ANN) approach the energy analysis of a domestic refrigerator using selected charges of LPG refrigerants (40, 50, 60 and 70 g) and different concentrations (0, 0.2, 0.4 and 0.6 gL−1) of TiO2-based nanolubricants as replacement for R134a refrigerant. The parameters for energy analysis include: compressor power consumption, cooling capacity, COP, compressor discharge temperature and pressure ratio. The findings showed that cooling capacity and COP of the domestic refrigerator using LPG refrigerant with TiO2 nanoparticles dispersed in a mineral oil lubricant was found to be higher than that of R134a by around 18.74–32.72 and 10.15–61.49%, respectively. Furthermore, compressor power consumption and pressure ratio of the domestic refrigerator using LPG refrigerant with TiO2–mineral oil lubricant were also found to be lower than that of R134a by about 3.20–18.1 and 2.33–8.45%, respectively, under similar conditions. The compressor discharge temperature was also found to be lower using LPG refrigerant with lubricant TiO2–mineral oil than R134a. The results further suggested that the best energetic performance of the domestic refrigerator was obtained using 40 g charge of LPG refrigerant with TiO2–mineral oil lubricant at 0.4 gL−1 of TiO2 concentration under similar operating conditions. The predictions from ANN models had excellent alignment with experimental results giving a range of values for R2 from 0.914 to 0.970, RMSE from 0.111 to 2.317, and MAPE from 0.865 to 3.148%.

Experiment and simulation study on performances of heat pump water heater using blend of R744/R290

The feasibility of applying natural eco-friendly blend of R744 (CO2) with R290 (propane) in a heat pump water heater (HPWH) system with large heat sink temperature lift was presented. The experiment and simulation investigations on the performances of the HPWH system using the R744/R290 blend and the one using R22 were carried out under variable operating conditions by using the water–water heat pump test rig and theoretical model, respectively. The experiment and simulation results indicate that the blend R744/R290 with mass fraction of 12%/88%, Mopt for short, is the appropriate substitute refrigerant for R22 in the HPWH system mainly because of its excellent performances such as superior heating COP and heating capacity and much lower compressor discharge temperature, etc. The heat source inlet temperature has striking effects on both the heating COP and the heating capacity, and the heat sink temperature lift has an obvious impact on heating COP but little impact on heating capacity.

Experimental investigation of a CO2 trans-critical cycle with IHX for chiller application and its energetic and exergetic evaluation in warm climate

This article presents comparative study of performance of a CO2 trans-critical chiller with and without internal heat exchanger (IHX), operating in warm climate (up to 45 °C) based on experimental data in energetic and exergetic perspective. Experiments are conducted following ARI guidelines and the results are presented for two sets of evaporator temperatures (−5°C and 0 °C) and for four different ambient temperatures (32 °C, 35 °C, 40 °C and 45 °C) for a range of gas cooler pressure within 80 to 110 bar. Also investigated is the effect of air flow velocity over gas cooler on the cycle performance. The optimal air velocity over the gas cooler is found to be near 1 m·s−1. Effect of fan efficiency on the fan power and COP are also presented. The experimental results demonstrate advantage of adoption of IHX in high ambient for chiller application. At high ambient (45 °C), the advantage of use of IHX is recorded to be 5.71% and 5.05% in energy and exergy efficiency respectively, at evaporator temperature of −5°C while the same are found 5.01% and 4.60% respectively, at evaporator temperature of 0 °C. Increase in compressor discharge temperature is also observed for IHX cycle. IHX is found to have the least contribution towards system irreversibility.

Study on energy saving effect of IHX on vehicle air conditioning system

In this paper, the performance of Internal Heat Exchanger (IHX) air conditioning system for R134a is investigated in bench test and vehicle test. Comparison for cooling capacity and energy consumption between IHX air conditioning system and traditional tube air conditioning system are conducted. The suction temperature and discharge temperature of compressor is also recorded. The results show that IHX air conditioning system has higher cooling capacity, the vent temperature decrease 2.3 °C in idle condition. But the suction temperature and discharge temperature of compressor increase 10°C. IHX air conditioning system has lower energy consumption than traditional tube air conditioning system. Under the experimental conditions in this paper, the application of IHX can significantly reduce the energy consumption of air conditioning system. At 25°C of environment temperature, AC system energy consumption decrease 14%, compressor energy consumption decrease 16%. At 37°C of environment temperature, AC system energy consumption decrease 16%, compressor energy consumption decrease 13%.

Performance computation of window air conditioner with very low GWP near azeotropic refrigerant mixtures as a drop in Substitutes to R22

The principal objective of the present study is to compute the thermodynamic performance of window air conditioner based on standard vapour compression refrigeration cycle using R22, R407C and nineteen refrigerant mixtures. In this work nineteen R290/R1270 blends at different compositions are developed. A MATLAB code is developed to compute the thermodynamic performance parameters of all the studied refrigerants at condensing and evaporating temperatures of 54.4°C and 7.2°C respectively. The performance parameters are cooling effect, compressor work, COP, compressor discharge temperature, power per ton of refrigeration and volumetric cooling capacity respectively. Analytical results revealed that COP of new binary mixture R290/R1270 (90/10 by mass %) is 2.82% higher among R22, R407C and nineteen studied refrigerants. Energy required by the compressor per ton of refrigeration for R290/R1270 (90/10 by mass %) is 2.73% lower among R22, R407C and nineteen studied fluids. The discharge temperature of the compressor for all the nineteen investigated blends are reduced by 6.0-8.9oC compared to R22. Overall thermodynamic performance of window air conditioner with R290/R1270 (90/10 by mass %) is better than R22 with significant savings in energy consumption and hence it is an energy efficient ecofriendly refrigerant mixture as a drop in substitute to R22.

Analytical computation of thermodynamic performance parameters of actual vapour compression refrigeration system with R22, R32, R134a, R152a, R290 and R1270

The present work focuses on analytical computation of thermodynamic performance of actual vapour compression refrigeration system by using six pure refrigerants. The refrigerants are namely R22, R32, R134a, R152a, R290 and R1270 respectively. A MATLAB code is developed to compute the thermodynamic performance parameters of actual vapour compression system such as refrigeration effect, compressor work, COP, power per ton of refrigeration, compressor discharge temperature and volumetric refrigeration capacity at condensing and evaporating temperatures of 54.4oC and 7.2oC respectively. Analytical results exhibited that COP of both R32 and R134a are 15.95% and 11.71% higher among the six investigated refrigerants. However R32 and R134a cannot be replaced directly into R22 system. This is due to their higher compressor discharge temperature and poor volumetric capacity respectively. The discharge temperature of both R1270 and R290 are lower than R22 by 20-26oC. Volumetric refrigeration capacity of R1270 (3197 kJ/m3) is very close to that of volumetric capacity of R22 (3251 kJ/m3). Both R1270 and R290 shows good miscibility with R22 mineral oil. Overall R1270 would be a suitable ecofriendly refrigerant to replace R22 from the stand point of ODP, GWP, volumetric capacity, discharge temperature and miscibility with mineral oil although its COP is lower.

Performance computation of window air conditioner with very low GWP near azeotropic refrigerant mixtures as a drop in Substitutes to R22

The principal objective of the present study is to compute the thermodynamic performance of window air conditioner based on standard vapour compression refrigeration cycle using R22, R407C and nineteen refrigerant mixtures. In this work nineteen R290/R1270 blends at different compositions are developed. A MATLAB code is developed to compute the thermodynamic performance parameters of all the studied refrigerants at condensing and evaporating temperatures of 54.4°C and 7.2°C respectively. The performance parameters are cooling effect, compressor work, COP, compressor discharge temperature, power per ton of refrigeration and volumetric cooling capacity respectively. Analytical results revealed that COP of new binary mixture R290/R1270 (90/10 by mass %) is 2.82% higher among R22, R407C and nineteen studied refrigerants. Energy required by the compressor per ton of refrigeration for R290/R1270 (90/10 by mass %) is 2.73% lower among R22, R407C and nineteen studied fluids. The discharge temperature of the compressor for all the nineteen investigated blends are reduced by 6.0-8.9oC compared to R22. Overall thermodynamic performance of window air conditioner with R290/R1270 (90/10 by mass %) is better than R22 with significant savings in energy consumption and hence it is an energy efficient ecofriendly refrigerant mixture as a drop in substitute to R22.

Analytical computation of thermodynamic performance parameters of actual vapour compression refrigeration system with R22, R32, R134a, R152a, R290 and R1270

The present work focuses on analytical computation of thermodynamic performance of actual vapour compression refrigeration system by using six pure refrigerants. The refrigerants are namely R22, R32, R134a, R152a, R290 and R1270 respectively. A MATLAB code is developed to compute the thermodynamic performance parameters of actual vapour compression system such as refrigeration effect, compressor work, COP, power per ton of refrigeration, compressor discharge temperature and volumetric refrigeration capacity at condensing and evaporating temperatures of 54.4oC and 7.2oC respectively. Analytical results exhibited that COP of both R32 and R134a are 15.95% and 11.71% higher among the six investigated refrigerants. However R32 and R134a cannot be replaced directly into R22 system. This is due to their higher compressor discharge temperature and poor volumetric capacity respectively. The discharge temperature of both R1270 and R290 are lower than R22 by 20-26oC. Volumetric refrigeration capacity of R1270 (3197 kJ/m3) is very close to that of volumetric capacity of R22 (3251 kJ/m3). Both R1270 and R290 shows good miscibility with R22 mineral oil. Overall R1270 would be a suitable ecofriendly refrigerant to replace R22 from the stand point of ODP, GWP, volumetric capacity, discharge temperature and miscibility with mineral oil although its COP is lower.

A comprehensive comparison between CO2 and Ethane as a refrigerant in a two-stage ejector-expansion transcritical refrigeration cycle integrated with an organic Rankine cycle (ORC)

In this paper, the performance of a two-stage ejector-expansion transcritical refrigeration cycle using ethane and CO2 as refrigerant is investigated. The theoretical analysis of cycle performance characteristics is carried out for both refrigerants from the first and second laws of thermodynamics viewpoints. Furthermore, a supercritical ORC is utilized for waste heat recovery of gas-cooler. Based on the results, it is found that the COP and second law efficiency for the ethane refrigerant are about 9.37 and 9.43% higher than that of the CO2. Moreover, the compressor discharge temperature for ethane compared to the CO2 in two-stage ejector-expansion transcritical refrigeration cycle is about 17–25% lower, which leads to a higher lifetime of the compressors for ethane. It is also concluded that the gas-cooler waste heat recovery improves the CO2 cycle performance more than ethane due to its higher potential for waste heat recovery.

Performance of low GWP R1234yf/R134a mixture as a replacement for R134a in automotive air conditioning systems

In this study, the performance of a new refrigerant, R1234yf/R134a (with a ratio of 89:11, by mass), was measured as alternative to R134a in automotive air conditioning systems using micro-channel heat exchangers in cooling and heating modes. Test results show that the capacities of R1234yf/R134a and R134a are similar in cooling and heating modes. The COP of R1234yf/R134a was lower than that of R134a by 4–9% in cooling mode, while it was lower by 4–16% in heating mode. The average compressor discharge temperature of R1234yf/R134a was up to 10°C lower than that of R134a in cooling and heating modes. By adding 11% R134a, R1234yf/R134a can be made virtually non-flammable. In addition, R1234yf/R134a has no ozone depletion potential, with a global warming potential of less than 150, thus meeting the requirement of European mobile air-conditioner directives. R1234yf/R134a can be used as an environment-friendly replacement for R134a in automotive air conditioning systems, with minor modifications.

Theoretical Computation of Performance of Sustainable Energy Efficient R22 Alternatives for Residential Air Conditioners

The present paper focuses on theoretical investigation of various new R22 alternatives. In this study R407C and four new R22 alternative refrigerant mixtures composed of R1270, R290, RE170, R134a and R32 at different compositions are considered. All the four new refrigerants possess zero ODP and low GWP compared to R22.The chief objective of the present work is to compute the thermodynamic performance of a standard vapour compression refrigeration cycle with R22 and its alternative refrigerants. A MATLAB code is developed to compute the thermodynamic performance of all the considered refrigerants. Thermodynamic analysis of all the refrigerants are evaluated at the condensing and evaporating temperatures of 54.4°C and 7.2°C respectively. The results showed that COP for the refrigerant mixture R134a/R1270/RE170 (55/37.5/7.5 by mass percentage) is 5.35% higher among the R22, R407C and four studied refrigerants. The compressor discharge temperature for R134a/R1270/RE170 (55/37.5/7.5 by mass percentage) is 11.9°C lower when compared to R22 and hence this mixture indicates the durability of the compressor life. The energy spent by the compressor per ton of refrigeration for the mixture R134a/R1270/RE170 (55/37.5/7.5 by mass percentage) is 5.12% lower among R22, R407C and four investigated refrigerants. The GWP of R134a/ R1270/ RE170 (55/37.5/7.5 by mass percentage) is 716 which is low compared to GWP of R22 (1760). Therefore R134a/R1270/RE170 (55/37.5/7.5 by mass percentage) is a sustainable energy efficient refrigerant to replace R22 used in residential air conditioners from the stand point of COP, compressor discharge temperature, energy savings, GWP and ODP. And also in this study thermodynamic performance of refrigerants are computed at various evaporating temperatures by keeping condenser temperature as constant.

Experimental study of R450A drop-in performance in an R134a small capacity refrigeration unit

The Kigali amendment to the Montreal Protocol has highlighted the hydrofluorocarbons (HFCs) phase out as a priority to reduce the future global mean temperature increase. R134a is the most abundant HFC in the atmosphere and therefore it must be substituted using environmentally benign alternatives. In the short term, blends of HFCs and hydrofluoroolefins can replace R134a. This paper experimentally evaluates R450A (GWP of 547), a non-flammable mixture of R1234ze(E) and R134a, in an R134a small capacity refrigeration system. The controlled experimental conditions cover evaporating temperatures from −15 to 12.5 °C and condensing temperature of 25, 30 and 35 °C (36 tests in total for each refrigerant). The experimental results showed that with only a thermostatic expansion valve adjustment the average R450A cooling capacity and COP are 9.9% and 2.9% lower than those measured using R134a. Besides, the observed compressor discharge temperature values of R450A are not greater than that of R134a.

Energy analysis of vapor compression refrigeration system using mixture of R134a and LPG as refrigerant

According to Kyoto protocol, R134a must be phased out soon due to its high global warming potential of 1430. In this work, an experimental investigation is carried out with R134a and LPG refrigerant mixture (composed of R134a and LPG in the ratio of 28:72 by weight) as an alternative to R134a in a vapor compression refrigeration system. Performance tests were performed under different evaporator and condenser temperatures with controlled ambient conditions. The results showed that the R134a and LPG refrigerant mixture has a higher coefficient of performance and lower compressor discharge temperature and pull down time as compared to R134a by about 15.1–17.82%, 2.10–13.86% and 1.01–5.90% respectively. Furthermore, the miscibility of R134a/LPG with mineral oil as a lubricant was also found good. In conclusion, the mixing refrigerant R134a/LPG proposed in this study seems to be an appropriate long-term candidate to replace R134a as a new generation refrigerant of VCRS, because of its well environmentally acceptable properties and its favorable refrigeration performances.