Suction Line Heat Exchanger Research Articles

Experimental study on the impact of indoor unit airflow velocity on the performance of an automotive heat pump system with a suction line heat exchanger

This study aimed to investigate the effect of changing the indoor unit air flow rate on the performance of an automobile heat pump with a suction line heat exchanger. Using a four-way valve, the automotive heat pump system was developed by reversing the refrigerant direction in the automobile air conditioning system, excluding the compressor. A suction line heat exchanger was added to the test system to enhance heat transfer between the liquid and suction lines of the automotive heat pump system. Performance comparisons were first performed for R134a and R1234yf by disabling the suction line heat exchanger. Then, the suction line heat exchanger was activated for R1234yf, and the tests were repeated. Performance comparisons were made for two different compressor speeds and three different indoor unit airflow speeds. It was found that using the heat exchanger in R1234yf operations improved the heating capacity, compressor discharge temperature and coefficient of performance by approximately 1.8 %, 5.1 % and 5.9 %, respectively. The heating capacity of the heat pump system using R134a, R1234yf, and R1234yf with the suction line heat exchanger was determined to be in the range of 2.46–3.29 kW, 2.35–3.04 kW, and 2.39–3.11 kW, respectively. An increase in the airflow speed of the indoor unit from 1.4 m s−1 to 3.2 m s−1 resulted in an average decrease of approximately 12.3 % in the compressor discharge temperature. In contrast, the heating capacity and coefficient of performance increased by approximately 11.8 % and 14.4 % on average, respectively, for R1234yf operations with the heat exchanger. This study revealed that by optimizing the air flow rate in the R1234yf heat pump system with a suction line heat exchanger, improvements in the heating capacity and coefficient of performance can be achieved, thus providing better thermal comfort in the passenger compartment.

Selection of working fluids and heat pump cycles at high temperatures: Creating a concise technology portfolio

As global efforts to address climate change intensify, industrial processes are of the highest interest due to their substantial contributions to greenhouse gas emissions and use of fossil energy. The deployment of high-temperature heat pumps (HTHPs) presents a significant potential for mitigating emissions and decreasing primary energy consumption in industrial applications. However, for widespread adoption, further technological development is crucial to enhance the technology's availability at higher supply temperatures. This study is dedicated to optimising HTHPs by exploring the intricate interplay between working fluids and heat pump cycle design, with the goal of establishing a technology portfolio that guarantees high performance across a wide range of high-temperature conditions. The research evaluates 16 working fluids in 10 HTHP configurations across a broad spectrum of high-temperature conditions, with source temperatures from 0 °C to 100 °C and temperature lifts from 20 K to 150 K. A polynomial estimating the Lorenz efficiency was proposed based on these configurations and temperature conditions. A portfolio of heat pumps using either isobutane, isopentane, or hexane, in a one-stage cycle layout with a suction line heat exchanger, a two-stage cycle layout with an open intercooler using R-718, and cascade configurations using these working fluids, consistently demonstrated the highest Lorenz efficiency for 95% of the evaluated temperature conditions. Including ammonia and carbon dioxide elevated this to 98% of temperature conditions, improving particularly at large sink temperature glides. While underscoring the necessity for an approach considering both COP and production costs, the study highlights the COP as the most important aspect. The marginal improvement observed by including HFOs highlights the potential of a natural working-fluid-based portfolio to achieve high performance, instilling optimism for the future of sustainable high-temperature heat pump applications.

Thermo-Economic Assessment of Advanced Triple Cascade Refrigeration System Incorporating a Flash Tank and Suction Line Heat Exchanger

Thermo-Economic Assessment of Advanced Triple Cascade Refrigeration System Incorporating a Flash Tank and Suction Line Heat Exchanger

Development and performance testing of a polyvalent heat pump for hot and cold water production

This research investigates a polyvalent heat pump that simultaneously produces hot and cold water and uses natural refrigerants. The novelty of using a 48 V direct current compressor driven by solar photovoltaic (PV) energy and the staged retrofitting improvements to this heat pump are discussed. Empirical testing has indicated that using a suction line heat exchanger yields a 30% improvement in the heating Coefficient of Performance (COP). Rising ambient temperatures could positively and negatively impact its heating and cooling performance, respectively. In addition, an average COP of 3.8 was obtained after a one-hour simultaneous mode operation, with the average hot tank temperature rising from 32.7 to 58.9°C and the average cold tank temperature dropping from 18 to 14.4°C. Being capable of operating the polyvalent heat pump under renewable energy sources and utilizing all its generated heating and cooling energy contributes further to the electrification and decarbonization of residential buildings.

Thermodynamic Analysis of Air Conditioning System for a Passenger Vehicle with Suction Line Heat Exchanger Using HFO-1234yf

In this study, the experimental thermodynamic performance and environmental impacts of a vehicle air conditioner using HFO-1234yf with a suction line heat exchanger are studied and compared with HFC-134a results. The influences of air flow rate and air temperature at the evaporator inlet, condenser side air face velocity, and the compressor speeds on the thermodynamic performance of the system are investigated. The results showed that HFO-1234yf has a 12% improved coefficient of performance with 8% higher exergy efficiency than HFC-134a. However, HFO-1234yf has marginally poor performance at higher compressor speeds due to more irreversibilities occurred in the compressor and evaporator. The average SLHX effectiveness was observed to be 45% for HFC-134a, while it was 41% for HFO-1234yf. The HFO-1234yf has a 33.9% and 29.4% and 45.1% lower total equivalent warming impact than HFC-134a for petrol, diesel, and liquefied petroleum gas vehicles, respectively. This study paves a way to promote the use of HFO-1234yf instead of HFC-134a without major modifications in the vehicle air conditioner unit.

Flow and heat transfer analysis of a domestic refrigerator with complex wall conditions

• A comprehensive numerical model with complex wall conditions for domestic refrigerators is developed and validated with experiments. • The flow and temperature distributions inside the compartments are discussed. • The impacts of the anti-condensation tube, VIPs and SLHX on the wall temperature and heat transfer are investigated. • The difference in heat leakage between with and without complex wall conditions reaches 6.2%. The heat transfer and temperature distributions inside the compartments and walls for a domestic refrigerator are vital to food storage and energy consumption. The refrigerator walls consist of many complex structural parts such as anti-condensation tube, vacuum-insulation panels (VIPs) and suction line heat exchanger (SLHX), which are closely related to the heat transfer. To investigate the influence of the complex walls on the heat transfer, this study presents a comprehensive numerical model for the domestic refrigerator with considering the complex wall conditions and an experiment is conducted to validate the accuracy of the model. The flow and temperature distributions inside the compartments are analyzed. The impacts of the anti-condensation tube, VIPs and SLHX on the wall temperature are investigated with and without complex wall conditions. The heat leakage through the walls of the refrigerator into the compartments from the environment is reported. The results show that the complex walls have a large impact on the heat transfer of the refrigerator. The difference in heat transfer between the two conditions with and without complex wall reaches 6.2%. The generic numerical model shows that the complex wall conditions should be considered when the manufacturers calculate the heat load and optimize the wall thickness to design a refrigerator.

Novel Numerical Modeling of Concentric and Lateral Capillary Tube Suction Line Heat Exchangers

Novel Numerical Modeling of Concentric and Lateral Capillary Tube Suction Line Heat Exchangers

The developing flow characteristics of water - ethylene glycol mixture based Fe3O4 nanofluids in eccentric annular ducts in low temperature applications

• The effect of nanofluids’ lower viscosity values on heat transfer was investigated. • Annular flow propagation of water-ethylene glycol based Fe 3 O 4 nanofluid was studied. • Maximum heat transfer enhancement was obtained for highest concentration. • Addition of the nanoparticles resulted in delay to reach steady-state conditions. • The performance evaluation criteria, pressure drop and exergy analysis were studied. Natural circulation loops with double pipe heat exchangers at heating and cooling ends have a potential to be used in the refrigeration systems as an alternative to suction line heat exchangers. The heat transfer capability of such natural circulation loops depends on the geometrical parameters as well as thermophysical properties of the working fluid. This study aims to investigate the effect of water-ethylene glycol mixture based Fe 3 O 4 nanofluids (0.01, 0.05 and 0.1 vol.%) on the annular flow propagation and heat transfer in the annuli of double pipe heat exchanger at low pressure side of the refrigeration cycle. In addition to increased non-dimensional velocity values due to the lower viscosity and higher non-dimensional temperature values with expanded temperature gradient, improved heat transfer by nanofluids shows that they can be used as secondary heat transfer fluids at low-pressure side in refrigeration systems. Although the maximum transferred (13.6% improvement compared to base fluid) heat observed for the highest concentration, the nanofluids with smallest concentration has the minimum pressure drop value (25% reduction compared to base fluid) and the highest performance evaluation criteria (PEC) value (PEC = 1.08) with tiny increase in exergy destruction (1.45% compared to base fluid).

Steady-state performance of capillary tubes for small-scale vapour compression systems using different refrigerants

• Fixed capillary tube geometry with straight, helical and SLHX sections. • A model was proposed to determine the steady-state operation of the capillary tubes. • Refrigerant velocity was shown to increase with the capillary tubes elongation. • Refrigerant outlet state of the capillary tube is determined. • Refrigerants R134a, R1234yf, R1234ze (E), R513A, R600, R600a are investigated. The operational performance of small-scale refrigeration systems is mainly decided by their capillary tubes outlet parameters, wherein an accurate determination of the pressure and vapour quality is a prerequisite. Experiments have been performed for a capillary tube (CT) with specified geometry consisting of a straight, a helical and a suction line heat exchanger (SLHX) section. The capillary tube is incorporated in a small refrigeration system operated with R600a. In addition, a model was developed to determine the steady-state operation of the capillary tubes (activated with R134a, R1234yf, R1234ze(E), R600, R600a, R152a and R513A refrigerants) and validated. The highest and lowest value of the vapour quality was discerned to be 0.3132 (for R1234yf) and 0.2124 (for R600), respectively. The relative errors between the experimental and model results for the CT outlet pressure and temperature were ranged from 1.16 to 5.35% and 0.12–0.81%, respectively. It is asserted that the present strategy may contribute towards the precise estimation of the pressure and vapour quality to customize the working performance of small scale refrigeration systems.

Investigation of performance improvement of a household freezer by using natural circulation loop

Growing number of household refrigerators and freezers also increase the overall energy consumption and number of household refrigerators have grown nearly 3% per year. On the other hand, investigations showed that household refrigerators have a significant technical energy saving potential of up to 30–40%. In this study, a single-phase natural circulation loop is considered as a suction line heat exchanger between the high and low pressure sides of conventional refrigeration cycle of a household chest freezer. The potential heat transfer by the single-phase natural circulation loop is studied by a CFD analysis, considering the possible temperature range for refrigeration cycle and geometrical parameters that affect the loop performance. The performance map of this refrigeration cycle is presented for different compressor suction and discharge pressures (LP/HP), discharge temperatures (T2) and different compressor speeds. The results indicate that the highest amount of heat transfer is obtained for the single-phase natural circulation loop with aspect ratio of 0.8 and pipe diameter of 6.53 mm. Moreover, the single-phase natural circulation loop provides 11.5% efficiency improvement for the household freezer for maximum compressor speed at lowest T2 and LP/HP. Considering reduction in required compressor work, SPNCmL assisted refrigeration system has a wider operating range.

OPTIMIZATION OF THE PERFORMANCE OF VAPOUR COMPRESSION CYCLE USING LIQUID SUCTION LINE HEAT EXCHANGER

One of the most commonly used refrigeration systems is vapour compression refrigeration system. As saving energy remains a challenge, researchers are putting a lot of efforts into finding efficient solution to improve the performance of vapour compression refrigeration systems. Mechanical subcooling and Liquid Suction Line Heat Exchanger (LSLHX) are approaches that have shown to improve the performance of Vapour Compression Cycle (VCC) systems. This experimental study is conducted to achieve two objectives. First objective is to optimize the heat source and heat sink water volumetric flow rate combination that results in the best performance. In order to evaluate the effect of using subcooling cycle and LSLHX cycle, different flow rate combinations are studied and analysed. Then, to optimize the heat source and heat sink water volumetric flow rate combination that outcome in the optimum performance. Second objective is to optimize the system performance through implementing subcooling and LSLHX. At the optimum water flow rates, the basic VCC performance of the designed system showed better performance compared to the published data. The system performance was improved by 10% at the optimum flow rate when solely subcooling was used while deteriorated by 47.5% at full LSLHX.

Performance ratings of concentric and lateral (taped, brazed and extruded) capillary tube suction line heat exchangers running with isobutane

This paper is aimed at studying the thermal performance of counterflow capillary tube suction line heat exchangers (CTSLHX) commonly used in household refrigerating appliances. Conventional and novel CTSLHX configurations, with different capillary tube and suction line geometries and made of different materials, were evaluated by means of a purpose-built testing facility designed to provide a strict control of the thermodynamic conditions of the refrigerant at the CTSLHX inlet ports. In total, 220 tests were performed with isobutane under typical operating conditions of household applications. The results pointed out that the extruded lateral configuration presented the highest thermal performance in terms of temperature effectiveness, followed by the lateral-brazed, the concentric, and the lateral-taped, respectively. Furthermore, it was also observed that the thermal performance of the latter is more affected by the tape tightness than that by its thermal conductivity.

Experimental studies on the performance of mobile air conditioning system using environmental friendly HFO-1234yf as a refrigerant

In this work, the experimental investigation on the performance and exergy analysis of mobile air conditioning system with suction line heat exchanger using environmental friendly HFO-1234yf was carried out under varied evaporator air flow rates. The performance was compared with existing HFC-134a results. The performance analysis showed that the cooling capacity and the coefficient of performance of the system with HFO-1234yf were lower than that of the HFC-134a by upto 2–11%. The power consumption and the volumetric efficiency of the compressor with HFO-1234yf were found to be 14.02% and 11.2% higher than that of HFC-134a. From the exergy analysis, it was observed that the major exergy destruction occurred in the compressor, followed by the condenser, evaporator, thermostatic expansion valve, and suction line heat exchanger for both refrigerants. The exergy efficiency of the system with HFO-1234yf was 2.4–12.6% lower than that of HFC-134a. From this study, it was observed that the losses experienced in the compressor, thermostatic expansion valve and evaporator lead to poor performance with HFO-1234yf.

Tuning thermostatic expansion valve for implementing suction line heat exchanger in mobile air conditioning system

The suction line heat exchanger is introduced in a mobile air conditioning system in order to achieve higher energy efficiency. Recent studies reveal that improvement in the system with suction line heat exchanger greatly depends on refrigerant properties and operating conditions. In this work, suction line heat exchanger was incorporated in a mobile air conditioning system and the spring force in the block-type thermostatic expansion valve of the modified system was adjusted (1) to match with the cooling capacity and (2) to match with the suction degree of superheat of the original system as two different cases. The refrigerant R134a was used in this study. The optimum charge of the mobile air conditioning system using R134a with suction line heat exchanger was experimentally found to be 740 g which was 19.4% higher than that of the original system. At optimum charge level before tuning the thermostatic expansion valve, the coefficient of performance (COP) of the system was increased by 2.8%, while the cooling capacity was reduced by 6%. After retuning the thermostatic expansion valve to match the original cooling capacity, the COP of the system improved by 11.8% with 10.5% lesser power consumption than that of the original system. With retuned thermostatic expansion valve for the original degree of superheating, the cooling capacity and COP of the system were increased by 6.7% and 16.2%, respectively. From this experiment, it is concluded that the mobile air conditioning system using R134a as a refrigerant with suction line heat exchanger performs better with suitable retuning of thermostatic expansion valve for the same degree of superheating than that is tuned for same cooling capacity.

Efficiency and Sustainability Improvement of Vapor Compression Configurations and a H2O/LiBr Absorption System Through Thermodynamic Analysis and Parameter Variation

The need for more efficient and sustainable refrigeration systems has promoted the development of new configurations. Subcooling have shown to improve the coefficient of performance whereas thermal energy driven configurations allow renewable sources to be employed. In this study thermodynamic models have been developed for simple, suction line heat exchanger, integrated and dedicated subcooling vapor compression systems using R-134a as the primary refrigerant and for a single-stage absorption refrigeration system with H2O/LiBr. The variation exhibited by the performance of the refrigeration systems is examined at various operating conditions finding that COP increases as condenser temperature decreases and evaporator temperature increases; high COP values are obtained with increasing generator temperature and LiBr concentration in the case of the absorption system. Low and zero emissions associated to subcooling strategies and absorption systems, due to the higher efficiencies and renewable character of the energy source respectively, were obtained when comparing the environmental impact.

Performance evaluation of a gas injection CO2 heat pump according to operating parameters in extreme heating and cooling conditions

The objective of this study is to optimize the performance of a gas injection CO2 heat pump according to the operating parameters in extreme heating and cooling conditions. The performances of CO2 heat pumps using a flash tank gas injection (FTGI) in the heating mode and FTGI with the suction line heat exchanger (FTSX) in the cooling mode are measured with the variations of the injection ratio, compressor frequency, and evaporating pressure in the extreme outdoor conditions. At the compressor frequency of 45 Hz, the cooling COP of the gas injection CO2 heat pump with the optimum injection ratio is 6.8% higher than that of the non-injection CO2 heat pump at the indoor/outdoor temperatures of 17/43 °C. Moreover, the heating COP of the gas injection CO2 heat pump is 7.1% higher than that of the non-injection system at the indoor/outdoor temperatures of 20/–15 °C.

An Experimental Study to Shaw the Effect of Capillary Tube – Suction Line Heat Exchanger on Refrigeration System Performance

An experimental study was investigated to show the effect of heat exchangers of capillary tube with suction line on compression refrigeration system performance which work on R-134a as refrigerant. Three types of heat exchangers (Coil, Concentric, Lateral) with capillary tube where made to use in refrigeration system. The experimental setup is measured for various volumetric flow rates for refrigerant, different air speeds for evaporator. So iterative method to find the actual process in capillary tube - suction line heat exchanger. The experimental results showed that at low refrigerant flow rate 15kg/hr, the maximum coefficient of performance for lateral heat exchanger which was 2.992 and minimum coefficient of performance for coil heat exchanger which was 2.876. While in case of high refrigerant flow rate 22.5kg/hr, the maximum COP for coil heat exchanger was 3.6, which was the highest value for all heat exchangers using in the system.

Experimental investigation on flow of R-600a inside a diabatic helically coiled capillary tube: Concentric configuration

This paper presents an experimental study of a diabatic flow of R-600a through a concentric configured helically coiled capillary tube suction line heat exchanger. The details of experimental facility for testing the diabatic capillary tube with different inlet sub-cooling degree and pressure are discussed. The effect of coil diameter, capillary length, capillary tube diameter, sub-cooling degree and inlet pressure on mass flow rate are presented. The degree of sub-cooling at the inlet of both straight and helical capillary tube is varied from 3–20 °C. In case of diabatic flow, the coiling reduces the mass flow rate of R-600a by 3–12 percent as compared to straight capillary tube. The refrigerant mass flow rate is scattered up with rise of pressure. A semi empirical correlation to predict the mass flow rate of R-600a flowing through a diabatic helical coiled capillary tube is proposed for sub-cooled inlet conditions. The proposed correlation predicts measured data with an error band of ± 20 percent.

Development of a continuous empirical correlation for refrigerant mass flow rate through non-adiabatic capillary tubes

Capillary tube, suction line heat exchangers (CT-SLHX) are widely used as expansion devices in small-capacity refrigeration and air-conditioning systems to enhance the refrigeration capacity and ensure that superheated refrigerant vapor enters the compressor. To calculate the mass flow rate through a capillary tube, a reliable non-adiabatic capillary tube model is necessary. Most previous correlations were developed separately for subcooled liquid inlet conditions and for saturated two-phase inlet conditions; so the models are not continuous at the saturated liquid point. An empirical model that is continuous at the saturated liquid point was developed and is introduced herein with a new dimensionless π parameter. This new empirical model is validated using experimental measurements available in the literature for the refrigerants R-134a, R-600a, R-410A, R-152a, and R-22. The new correlation shows good agreement with the experimental data.

Experimental Analysis of Suction Line Heat Exchanger by Using R-134a

Experimental Analysis of Suction Line Heat Exchanger by Using R-134a