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Investigation of thermal-flow characteristics of the minichannel heat exchanger of variable louvers height

Romaniak Artur, Kowalczyk Michał Jan, Łęcki Marcin, Gutkowski Artur, Górecki Grzegorz

Archives of Thermodynamics

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2023

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Vol. 44, no 3

119--141

EN

The numerical simulation of the heat transfer in the flow channels of the minichannel heat exchanger was carried out. The applied model was validated on the experimental stand of an air heat pump. The influence of louver heights was investigated in the range from 0 mm (plain fin) to 7 mm (maximum height). The set of simulations was prepared in Ansys CFX. The research was carried out in a range of air inlet velocities from 1 to 5 m/s. The values of the Reynolds number achieved in the experimental tests ranged from 93 to 486. The dimensionless factors, the Colburn factor and friction factor, were calculated to evaluate heat transfer and pressure loss, respectively. The effectiveness of each louver height was evaluated using the parameter that relates to the heat transfer and the pressure drop in the airflow. The highest value of effectiveness (1.53) was achieved by the louver height of 7 mm for the Reynolds number of around 290.

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Experimental investigation of the energy efficiency of a linear compressor and comparison with a reciprocating compressor in a small refrigeration system

Kowalczyk Michał Jan, Romaniak Artur, Łęcki Marcin, Gutkowski Artur, Górecki Grzegorz

Archives of Thermodynamics

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2023

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Vol. 44, no 4

243--260

EN

The conducted experimental studies of the linear compressor concerned the cooling capacity, efficiency, and Energy Efficiency Ratio (EER). Linear compressor performance tests were carried out for the supply voltage of 190–265 V and the supply frequency in the range of 45–65 Hz, which allowed the compressor to be tested outside its typical operating range. Modulation of the performance was achieved using an inverter. The full range of performance characteristics of a linear compressor was presented. The results were compared with a reciprocating compressor for similar displacement volume, which achieved lower EER values by an average of 38% for a pressure ratio above 1.7. The power consumption of a linear compressor is on average two times lower than that of a reciprocating compressor.

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Investigations of thermal-flow characteristics of minichannel evaporator of air heat pump

Kowalczyk Michał Jan, Łęcki Marcin, Romaniak Artur, Warwas Bartosz, Gutkowski Artur

Archives of Thermodynamics

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2021

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Vol. 42, no 4

261--279

EN

The results of experimental investigations of heat transfer and a friction factor in an air channel of the minichannel heat exchanger are presented. The main aim of the analysis was to examine an influence of geometrical parameters of the fin shape with two geometries on heat transfer and flow characteristics of the air channel. The test rig was designed to monitor the parameters of the airflow during cooling by the minichannel heat exchanger. The analysis was conducted with the airflow in the range of 1–5 m/s. The temperature of the evaporation in a refrigeration system was set at 288.15 K. The energy balance of the refrigeration system was carried out. A numerical model describes the airflow through a part of the heat exchanger. Numerical simulations were validated with the experimental data. Numerical methods were used to evaluate the performance of the system and possibilities to improve the fin geometry. The characteristics of the friction factor (a measure of the pressure loss in the airflow) and the Colburn j-factor (heat transfer performance) were calculated. For the maximal velocity of the airflow, the Colburn factor was equal to 0.048 and the evaporator capacity equaled 1914 W.