Ki-Dong Son

Bio: Ki-Dong Son is an academic researcher from Pusan National University. The author has contributed to research in topics: Refrigerant & Heat exchanger. The author has an hindex of 3, co-authored 5 publications receiving 31 citations. Previous affiliations of Ki-Dong Son include LG Electronics.

An assessment of models for predicting refrigerant characteristics in adiabatic and non-adiabatic capillary tubes

Abstract: Small vapor compression refrigeration systems incorporate a non-adiabatic capillary tube called a capillary tube-suction line heat exchanger (SLHX) in order to improve performance. The thermodynamic properties of the refrigerant in the capillary tube and suction pipe are influenced by associated phenomena. This study compares various relevant models. Based on the comparison recommended correlations were selected and the simulation results show that the friction factor model has the most dominant.

An evaluation of constituent correlations for predicting refrigerant characteristics in adiabatic capillary tubes

Abstract: Capillary tubes are widely used as a refrigerant flow control device in small refrigeration systems. Since the flow behavior inside the capillary tube is complex, many physical models are necessary to predict the characteristics of the refrigerant flow in a capillary tube. In the present paper, refrigerant flow characteristics inside the capillary tube have been studied to find out recommended empirical correlations of influential parameters. A numerical capillary model is developed to predict the refrigerant characteristics. Various empirical correlations regarding single-phase friction factor, two-phase viscosity, two-phase frictional multiplier and metastable flow are examined using this numerical capillary model. Calculated results are compared with experimental data to examine the accuracy in terms of required capillary tube length and mass flow rate. Based on the comparison, recommended correlations are selected to be used for capillary flow analysis.

Simulation of the Effects of a Non-Adiabatic Capillary Tube on Refrigeration Cycle

Abstract: The simulation of refrigeration cycle is important since the experimental approach is too costly and time-consuming. The present simulation focuses on the effect of capillary tube-suction line heat exchangers (CT-SLHX), which are widely used in small vapor compression refrigeration systems. The simulation of steady states is based on fundamental conservation equations of mass and energy. These equations are solved simultaneously through iterative process. The non-adiabatic capillary tube model is based on homogeneous two-phase model. This model is used to understand the refrigerant flow behavior inside the non-adiabatic capillary tubes. The simulation results show that both of the location and length of heat exchange section influence the coefficient of performance (COP). These results can be used in either design calculation of capillary tube length for refrigeration cycle or effect of suction line heat exchanging on refrigeration cycle.

A Simulation for Predicting the Refrigerant Flow Characteristics Including Metastable Region in Non-Adiabatic Capillary Tubes

Abstract: The capillary tube/suction line heat exchanger (SLHX) is widely used in small refrigeration systems. The refrigerant flowing in the SLHX experiences frictional and accelerational head losses, flashing, and heat transfer simultaneously. The simulation of refrigerant flow through SLHX is important since this will help engineers analyze and optimize the SLHX incorporated in a refrigeration system. The present SLHX model is based on conservation equations of mass, momentum and energy. Also a meta-stable model is included. All these equations are solved simultaneously. In this paper, HFC-134a refrigerant flow through a non-adiabatic capillary tube is simulated. The simulation results are discussed but not validated against experimental measurements yet.

Simulation of the Refrigeration Cycle Equipped with a Non-Adiabatic Capillary Tube

Abstract: The simulation of refrigeration cycle is important since the experimental approach is costly and time-consuming. The present paper focuses on the simulation of a refrigeration cycle equipped with a capillary tube-suction line heat exchanger(SLHX), which is widely used in small vapor compression refrigeration systems. The present simulation is based on fundamental conservation equations of mass, momentum, and energy. These equations are solved through an iterative process. The non-adiabatic capillary tube model is based on homogeneous two-phase flow model. This model is used to understand the refrigerant flow behavior inside the non-adiabatic capillary tube. The simulation results show that both of the location and length of heat exchange section influence the coefficient of performance (COP).

Development of empirical correlations for non-adiabatic capillary tube based on mechanistic model

Abstract: Capillary tubes play a vital role in the refrigeration cycle, as they reduce the temperature of the refrigerant. The non-adiabatic capillary tube (capillary tube-suction line heat exchanger: CT-SLHX) is widely incorporated into small refrigeration systems to enhance the cooling performance and ensure that only the refrigerant vapor enters the compressor. It is necessary to develop an accurate and fast-running non-adiabatic capillary tube model, as the performance of the refrigeration cycle simulation tool is largely dependent on the accuracy and run-time its component models. In the present study, a reliable mechanistic model was used to generate reference data. An empirical model was developed based on the data produced by this mechanistic model. This new empirical model was validated against experimental measurements available in the literature for R-134a and R-600a. The new model is fast-running and its performance metrics are in good agreement with experimentally measured data.

Heat pump control method based on direct measurement of evaporation pressure to improve energy efficiency and indoor air temperature stability at a low cooling load condition

Abstract: The control systems of conventional heat pumps have an input of refrigerant temperature at the evaporator outlet to maintain superheat at proper level. In order to develop a control method that can be used to achieve better indoor thermal comfort and energy efficiency at a low cooling load condition than the current control method, a new method of the evaporation pressure control based on the evaporator outlet pressure reading (EPCP) was developed. The changes in the stability of indoor air temperature and power consumption were measured while changing the compressor frequency in accordance with the new control method. Compared with the evaporation pressure control based on the evaporator outlet temperature reading, the EPCP control method appeared to improve the stability of room air temperature or occupant thermal comfort significantly.

A Review of Prediction Methods for Two-Phase Pressure Loss in Mini/Micro-Channels

Abstract: Previous methods and correlations for predicting two-phase frictional pressure loss in mini/micro-channels are reviewed and compared. The empirical correlations are classified into four groups of modeling approaches: Homogeneous equilibrium models (HEMs), separated flow models (SFMs), direct empirical correlations, and flow pattern specific correlations. In order to examine the characteristics of the predictive methods for two-phase pressure loss in mini-channels and to assess the accuracy of the previous models and correlations, extensive experimental data and correlations that are available in the open literature are collected. The 1175 and 1304 experimental data for the two-phase pressure drop for condensing and boiling flows, respectively, are gathered from 15 papers and reports. The results present that the size of the channel significantly influences the pressure drop. The comparison demonstrates that Cicchitti et al.’s two-phase viscosity model is recommended for predicting two-phase pressure loss when the HEM is used. In general, the SFM with the two-phase multipliers of Muller–Steinhagen and Heck and Kim and Mudawar outperforms others for channel diameters of less than 3mm.

Use of Artificial Neural Network approach for depicting mass flow rate of R134a /LPG refrigerant through straight and helical coiled adiabatic capillary tubes of vapor compression refrigeration system

Abstract: In this work, an experimental investigation carried out with R134a and LPG refrigerant mixture for depicting mass flow rate through straight and helical coil adiabatic capillary tubes in a vapor compression refrigeration system.Various experiments conducted under steady-state conditions, by changing capillary tube length, inner diameter, coil diameter and degree of subcooling. The outcomes demonstrated that mass flow rate through helical coil capillary tube discovered lower than straight capillary tube by about 5−16%. Dimensionless correlation and Artificial Neural Network (ANN) models developed to predict the mass flow rate. It found that dimensionless correlation and ANN model predictions concurred well with experimental results and brought out an absolute fraction of variance of 0.961 and 0.988, root mean square error of 0.489 kg/h and 0.275 kg/h and mean absolute percentage error of 4.75% and 2.31%, respectively. The outcomes suggested that ANN model shows better statistical prediction than dimensionless correlation model.

An assessment of models for predicting refrigerant characteristics in adiabatic and non-adiabatic capillary tubes

Abstract: Small vapor compression refrigeration systems incorporate a non-adiabatic capillary tube called a capillary tube-suction line heat exchanger (SLHX) in order to improve performance. The thermodynamic properties of the refrigerant in the capillary tube and suction pipe are influenced by associated phenomena. This study compares various relevant models. Based on the comparison recommended correlations were selected and the simulation results show that the friction factor model has the most dominant.