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Energy efficiency and the amount of refrigerant in heat exchangers used in cooling systems has recently been an important research subject. In this study, in order to compare and analyze different types of evaporators, industrial refrigerators were designed and in this context, test setups in accordance with TS EN ISO 23953-2 standard were produced. R290 (propane) was used as the refrigerant in the designed system. During the experiment, temperature-pressure measurements were taken at a certain point in the cooling system equipment of the products, which were cooled every minute, and test data were recorded. As a result of the data obtained from the experimental results, while the temperature difference of the air entering and leaving the evaporators was 6.797 in the first system using ½" tube diameter evaporator, it was calculated as 7.052 in the corrugated and hydrophilic coated second system using 3/8" tube diameter. In the experimental setups, the energy consumed in the first and second systems and the masses of R-290 refrigerant were measured as 24.64 kWh, 23.39 kWh and 700 grams, 430 grams, respectively. Consequently, it was calculated that the second system was 5.073% and 38.57% more efficient in terms of energy efficiency and the refrigerant mass used. Coefficient of performance values for the first and second systems were found as 2.807 and 3.013, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The effects of the subcooling heat exchanger (SCHX) on the performance of the multi-split variable refrigerant flow (VRF) system with long pipe were investigated in a field test during the cooling season. By varying the refrigerant mass flow rate via the electronic expansion valve, the degree of subcooling was controlled. It was found that VRF system with SCHX improved the cooling performance factor (CPF) about 8.5% under similar outdoor temperature profiles, as compared to the baseline without SCHX. However, when the fraction of total refrigerant that passes through the SCHX was higher than 5.27%, the CPF starts to decrease due to the decreased refrigerant mass flow rate through the evaporators. Employing a SCHX in a VRF system with long pipe was found to be an effective method for improving the system performance and reliability. [Copyright &y& Elsevier]

This technical note communicates the thermal performance of a modified ten-Ton Refrigerant Direct Expansion (10-TR DX) air conditioning unit into a chiller under actual operating conditions. The modified unit achieved higher COP and cooling capacity compared with conventional DX. The increase in the unit cooling capacity is basically attributed to the enhanced heat transfer coefficient of the Plate-and-Frame Heat Exchanger evaporator. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The efficient operation of a solar cooling system strongly depends on the chiller behavior under part load conditions, since driving energy and cooling load are never constant. For this reason, the performance of a single stage, hot water driven 30 kW H2O/LiBr-absorption chiller employed in a solar cooling system with a field of 350 m² evacuated tube collector has been analyzed under part load conditions with both simulations and experiments. A simulation model has been developed for the whole absorption chiller (Type Yazaki WFC-10), where all internal mass and energy balances are solved. The connection to the external heat reservoirs of hot, chilled, and cooling water is done by lumped and distributed UA values for the main heat exchangers. In addition to an analytical evaporator model-which is described in detail-experimental correlations for UA values have been used for the condenser, generator, and solution heat exchanger. For the absorber, a basic model based on the Nusselt theory has been employed. The evaporator model was developed, taking into account the distribution of refrigerant on the tube bundle, as well as the change in operation from a partially dry to an overflowing evaporator. A linear model is derived to calculate the wetted area. The influence of these effects on cooling capacity and coefficient of performance (COP) is calculated for three different combinations of hot and cooling water temperature. The comparison to experimental data shows a good agreement in the various operational modes of the evaporator. The model is able to predict the transition from partially dry to an overflowing evaporator quite well. The present deviations in the domain with high refrigerant overflow can be attributed to the simple absorber model and the linear wetted area model. Nevertheless, the results of this investigation can be used to improve control strategies for new and existing solar cooling systems. [ABSTRACT FROM AUTHOR]