Design Parameters Of Heat Exchanger Research Articles

Simulation of continuous thermally regenerative electrochemical flow cycle and coupled with photovoltaic/thermal system

Thermally regenerative electrochemical cycle (TREC) is an efficient, clean and feasible low-temperature thermoelectric conversion technology. Coupling it with flow battery (FB) can not only achieve continuous operation, but also can be used to realize the heat energy recovery of the photovoltaic/thermal (PV/T) system. In this paper, a continuous TREC-FB system including two charging-free cells is proposed for outputting power at both high and low temperatures. An electrochemical-thermodynamic coupling algebraic model is established to explore the effects of electrolyte flow rate, temperature difference and design parameters of heat exchanger on the power density (PTREC) and thermoelectric efficiency (ηele,TREC) of the TREC-FB. Experimental study on TREC-FB is carried out for model validation. The results show that PTREC is determined by the temperature difference and the electrolyte flow rate, which contribute to enhanced voltage and mass transfer, respectively. For specific heat source scenarios, the ηele,TREC is mainly affected by the flow rate, followed by the heat transfer area AH, and finally is the flow channel height and the thermal conductivity of the heat exchanger. Moreover, for the continuous TREC-FB-PV/T coupled system, the energy conversion efficiency reaches an average of 11 % within one day by optimizing the designed temperature difference.

Effect of triangular perforated flat cone-shaped inserts on performance of double-tube heat exchanger

This study investigated the effect of triangular perforations with flat conical inserts in a double-tube heat exchanger. Triangular perforations with flat cone-shaped inserts were placed inside the inner tube to enhance the heat transfer coefficient. The experiments were conducted for a number of flat conical strips (m) and pitch ratios (P = p/di) for flows varying from Re = 3000 to 9000 at a constant attack angle (α = 20°). The results showed that a triangular perforation with flat cone-shaped inserts remarkably increases the heat transfer factor, in contrast to flat conical inserts. The rise in the coefficient of heat was attributed to the creation of turbulence and disturbance of the boundary layer caused by perforated inserts. Furthermore, it was observed that the heat transfer coefficient increased with the Reynolds number, indicating that the effect of the inserts was more significant at higher fluid velocities. Correlations were developed to compare and analyze the results of the Nusselt number and friction factor. The developed correlation results are in good agreement with the experimental results. The findings obtained from this study can be implemented to enhance the performance and optimize the design parameters of industrial heat exchangers.

A Study on the Relationship of Heat Exchanger Design Parameters with Water Lily Stem Profile by Robust Statistical Method

The study has successfully modeled and simulated a polymorphic tube based on the water lily stem using the robust statistical method and software. Taguchi analysis shows that the size factor E (Cross-section length of inner hole) with the effects values 39.89% has the most significant influence on the response temperature difference ((Δt) 0C). The size factor A (Peduncle diameter) has the most critical influence on the response pressure difference (ΔP (Pa)), with an effect value of 42.88%. The size factor C (Large inner hole diameter) with the significant effect value of 34.78% affects the response velocity difference (Δv (m/s)) the most. By ANOVA analysis, the results of response temperature difference analysis show that both the T-value and P-value of the size factor E (Cross-section length of inner hole) reach values that satisfy the setup requirements, with T-value reaching the most significant T-value 3.85 and the P-value 0.043 being smaller than the benchmark value 0.05, the final result indicated the size factor E (Cross-section length of inner hole) is the factor that has the most significant influence on the temperature difference of the model. For pressure difference, the results show that both the T-value and P-value of the size factor A (Peduncle diameter) reach values that satisfy the setup requirements, with the T-value reaching the largest T-value 12.19 and P-value 0.001 being smaller than the benchmark value of 0.05, the size factor A (Peduncle diameter) is the factor that has the most significant influence on the pressure difference of the model. For velocity difference, the results show that both the T-value and P-value of the size factor C (Large inner hole diameter) reach values that satisfy the set requirements, with the T-value reaching the largest T-value of 3.72 and the P-value 0.047 being smaller than the benchmark value 0.05, the size factor C (Large inner hole diameter) is the factor that has the most significant influence on the velocity difference of the model. Minitab software verification based on the Means graph drawn by Minitap17 software, the results show the best combination for response temperature difference is A3-B2-C1-D2-E2. Similarly, the best combination for response pressure and velocity differences is A2-B2-C3-D1-E1 and A2-B3-C2-D1-E3, respectively.

열교환기 최적 설계를 통한 친환경 냉동탑차용 냉동시스템의 성능향상 연구

An analytical study on the optimization of heat exchanger design parameters of a refrigeration system for a one-ton eco-friendly refrigerator truck was conducted to improve its performance. The components of the refrigeration system were modeled analytically. The developed model was validated by comparing the predicted values with the measured data. The effects of the major design parameters on system performance were analyzed using the developed model. The heat exchangers were optimized according to the geometric parameter to improve system efficiency. The COP of the optimized refrigeration system was an average of 12.5% higher than that of the conventional system. Additionally, a drop-in simulation for the optimized refrigeration system using R455A was conducted to determine an alternative for R404A. The COP of the refrigeration system with R455A (COPR455A) was almost the same as that of the refrigeration system with R404A (COPR404A) because the increase in the heat transfer rate was the same as that of the compressor work. However, the COPR455A was 8.7% higher than the COPR404A at the same heat transfer rate.

Thermal Condition in the Channels of Plate Heat Exchangers

Equipping heat points with plate-type heat exchangers is an integral structural element of the 3rd generation heat and power network and a component of the reliability of the heat supply system as a whole. It has been established that the optimization calculations of heat exchangers of this type are difficult due to the absence of dependences on heat transfer and hydraulic resistance between the channels in the structural space of the heat exchanger.Purpose of research. To clarify the method of calculating plate heat exchangers, excluding the equality of thermal and hydraulic conditions from the generally accepted assumptions.Methods. The research methodology is based on the use of the law of conservation of mass in order to determine the temperature parameters of working fluids in each channel. The solution of this problem is proposed in the form of a system of equations, each of the equations of which characterizes the thermal balance of the channel under consideration. A computer model of the heat exchanger is constructed in order to conduct a numerical study of the thermal regime of the heat exchanger.Results. It is indicated that as an assumption in the well-known mathematical model for calculating the thermal regime of a plate-type heat exchanger, the condition of equal distribution of fluid flows between channels is accepted. This restriction leads to equalization of liquid temperatures in each channel. Taking into account the geometric arrangement of the channels, the excess of the final temperature of the heating and heated coolant in the first and last channels with respect to known data is up to 10%. The results of the study confirm the hypothesis of uneven heating of the coolant along the length of the plate package due to the uneven flow distribution between the channels.Conclusion. The results of analytical calculation and modeling in the SolidWorks environment of the temperature regime in the channels of a plate-type heat exchanger indicate a significant influence of the geometric arrangement on the thermal regime in the channels. The formulated provisions of the mathematical description of the unevenness of the thermal regime of heat exchange channels, taking into account the location of the plates, are recommended to be used when improving the design parameters of plate-type heat exchangers.

Energy-saving installation for heating and cooling livestock premises using geothermal energy

The article considers the calculation of the main design parameters of a geothermal air cooling system in livestock premises, which, unlike traditional systems, do not use fossil fuels to generate heat. They simply take energy from the soil, while, as a rule, electricity is used only for the operation of fans, compressors and pumps. The purpose of the study is to reduce energy consumption when creating the technologically necessary temperature and humidity conditions in premises by using the cold of the earth’s strata. The calculation of the heat exchanger installed inside the livestock premises is reduced to the choice of design and energy parameters of the surface heat exchanger of the cooling unit, as well as to the determination of the flow rate of water passing through the heat exchanger. Water cooling is done in a heat exchanger buried vertically in the soil (the so-called probe). The probe is a plastic pipe lowered into the well and filled with a special filling with good thermal conductivity. The article presents the calculation of the probe length, since this parameter of the heat exchanger-probe is the main parameter of the installation.

Parametric study of low-temperature thermal energy storage using carbon dioxide as the phase change material in pillow plate heat exchangers

Industrial low-temperature freezing applications are often batch processes, requiring a lot of energy, exerting stress on the electrical grid. To relieve this stress, thermal energy storage can be used. However, there is a lack of suitable storage material for low temperature applications (around −50 °C). Under high pressures, carbon dioxide can be used as the phase change material for storage temperatures around −55 °C. In this study, a parametric study was conducted on the design and operational parameters of an industrial-scale pillow plate heat exchanger with carbon dioxide. Two responses were selected for the analysis where R1 considered the storage size over the phase change time (kWh/h), while R2 indicated the cost over the storage size (USD/kWh). Using design of experiments, a total of 52 simulations were carried out to investigate the parameters under constant heat transfer surface area. Analysis of variance was then carried out followed by correlation development and optimization. It was found that regardless of the process (charging or discharging), for R1 and R2, the difference between refrigerant and carbon dioxide phase change temperatures followed by plate material had the highest significance. In contrast, the refrigerant flow rate had the lowest significance in almost all cases. Moreover, considering an equal weight for the responses, overall optimal conditions were determined for the processes. The recommended values for plate pitch, plate material, difference between refrigerant and carbon dioxide phase change temperatures and refrigerant flow rate were 25 mm, aluminum, 15 °C and 4 kg/s, respectively.

EFFECT OF KEROSENE MASS FLOW RATE AND AVERAGE TEMPERATURE IN DIRECT CONTACT HEAT EXCHANGER

Industrial plants are huge consumers of energy, these plants are installing heat exchangers in an effort to reduce energy consumption, and so improve operating efficiencies. Limited numbers of experimental and numerical investigations have dealt with the parameters affecting the heat transfer aspects in single phase direct contact heat exchangers which may be selected for their high thermal efficiency and minimum capital investment. In oil refineries energy from hot temperature oil streams can be recovered by transfer directly to a cheap coolant liquid in liquid-liquid direct contact heat exchangers. The heat recovered from these heat exchangers has different applications including preheating boiler feed water and preheating wash water. Heat recovery from hot temperature refinery products using direct contact heat exchanger throughout a theoretical phenomenological study is central to the theme of this paper. Kerosene-water system has been chosen. The effect of the heating fluid inlet temperature (65-97.50)°C, and mass flow rate (25 to 45) kg/s on direct contact heat exchanger design parameters and heat transfer characteristics were investigated theoretically throughout nine cases. Correlations of heat recovered from the system as well as design and operating characteristics of the heat exchanger were estimated. Increasing kerosene flow rate found to associate directly with increasing the contact surface area, number of plates, number of channels per pass and pressure drop, while when the heat exchanger is designed to operates at high kerosene inlet temperature, big heat exchangers with large areas, high number of plates and channels per pass are needed for efficient heat exchanger performance. Optimization and modeling the effect of kerosene operating variables on heat recovered was conducted using Response Surface Methodology. The results showed that an optimum heat recovery value of 6.8782 megawatt could be achieved for kerosene optimum inlet temperature (91.82°C), and mass flow rate (50.11 kg/s). Keywords: direct contact heat exchanger; kerosene and water system, kerosene mass flow rate and inlet temperature.

A new indicator for minimizing size of an ORC power plant based on heat exchanger and turbine design parameters

• System size index SSI – a novel indicator for minimizing size of the ORC is proposed. • SSI is defined based on heat exchanger area and turbine rotor diameter. • By using heat transfer indicators, the turbine may be oversized by up to 70%. • With the use of turbine indices, the heat exchanger may be oversized by up to 40% . • By applying the SSI index, the ORC components are sized optimally. The increasing interest in mobile applications and modular structures of an organic Rankine cycle (ORC) has resulted in growing importance of the optimal sizing of the ORC installation. Most of the existing works were focused on reducing dimensions of the ORC by applying indicators estimating size of a single type of the ORC component. This study aims to define an indicator which comprehensively evaluates the size of the ORC power plant. The proposed indicator, specified as System Size Index SSI , is formulated based on two key ORC design parameters, namely the total heat transfer area of the heat exchangers and the rotor diameter of the turbine. To examine the versatility of SSI , the analysis was conducted considering different ORC applications scenarios, including modular geothermal power plants and mobile waste heat recovery units. The findings of single-objective optimization procedures have shown that by applying indicators evaluating size of the heat exchangers, the turbine rotor diameter may deviate from its smallest possible dimension by up to 70%. Similarly, by utilizing indices evaluating size of the turbine, the heat exchangers area may differ from its optimal size by up to 40%. Meanwhile, by using the SSI indicator, both the total heat transfer area and turbine rotor diameter did not differ from their smallest possible dimensions by more than 1% for each scenario considered. Finally, based on a bi-objective analysis with SSI and net power output as the criteria, it was concluded that by applying such indicators as APR parameter or performance factor PF , the designer is left with a single design solution, while the adoption of the bi-objective approach gives much more flexibility in finding a compromise between the system size and power output of the installation.

Influence of Heat Exchanger Design on the Thermal Performance of a Domestic Wine Cooler Driven by a Magnetic Refrigeration System

Conventional and not-in-kind refrigerators require heat exchangers for their operation. Yet, most magnetic cooling studies do not take full account of those components despite their importance in defining the cooling capacity and temperature span. To investigate the influence of heat exchanger design parameters on the performance of magnetic refrigerators, a model was developed to integrate the heat exchangers, regenerators and thermal reservoirs. The results were compared with data generated in an apparatus that emulates the conditions of the thermal fluid supplied by the regenerators to a cold heat exchanger positioned inside the cabinet of a retrofitted 130-liter wine cooler. Six tube-fin heat exchangers were evaluated to identify the most suitable geometry (number of tube rows and fin density) for the compact magnetic refrigerator. Numerical simulations described the influence of the heat exchanger on the regenerator performance in terms of the liquid stream effectiveness. For a temperature span of 20°C between the external environment and the refrigerated compartment, the best heat exchanger/fan assembly resulted in a cooling capacity reduction of 37\% and a temperature span increase of 32\%, in comparison with an idealized system. The expected system coefficient of performance (COP) and second-law efficiency were 1.8\% and 13\%, respectively.

New thermal-hydraulic correlations for printed circuit heat exchangers (PCHEs) with zigzag channels under high Reynolds numbers

PurposeThe purpose of this paper is to investigate the impact of semi-circular zigzag-channel printed circuit heat exchanger (PCHE) design parameters on heat transfer and pressure drop of flows under high Reynolds numbers and provide new thermal-hydraulic correlations relevant to conditions encountered in natural gas processing plants.Design/methodology/approachThe correlations were developed using three-dimensional steady-state computational fluid dynamics simulations with varying semicircular channel diameter (from 1 to 5 mm), zigzag angle (from 15° to 45°) and Reynolds number (from 40,000 to 100,000). The simulation results were validated by comparison with experimental results and existing correlations.FindingsThe results revealed that the thermal-hydraulic performance was mostly affected by the zigzag angle, followed by the ratio of the zigzag channel length to the hydraulic diameter. Overall, smaller zigzag angles favored heat transfer intensification while keeping reasonably low pressure drops.Originality/valueThis study is, to date, the only one providing thermal-hydraulic correlations for PCHEs with zigzag channels under high Reynolds numbers. Besides, the broad range of parameters considered makes the proposed correlations valuable PCHE design tools.

Parametric study of air-cooled TEG heat exchanger design for waste heat recovery in heavy-duty vehicle

This study focuses on the influence of different heat exchanger (HX) design parameters like the fin height, fin number, and fin thickness on the performance of an air-cooled exhaust gas thermoelectric generator (TEG). The TEG is considered to be installed on a heavy-duty truck traveling at 85 km/h on the highway thus ensuring the required cooling air for the cold side HX. It was found that the number of fins has the highest influence on the amount of extracted heat and power output of the system, but it also negatively affects the pressure drop. Increasing the fin height improves the pressure drop, but the performance increase is limited. Similarly, increasing the fin thickness provides only limited output improvements, but it also affects the pressure drop. Finally, compared to the hot side HX, the cold side HX has a limited influence on TEG output, but its design is not restricted by the pressure drop.

A new method to multi – objective optimization of shell and tube heat exchanger for waste heat recovery

ABSTRACT Nowadays, fossil energy sources are decreasing gradually and environmental problems are increasing thus energy savings are among the current topics. In this context, determining the optimum design parameters of heat exchangers can provide significant savings during the economic life of waste heat recovery systems. However, due to discrete decision variables, highly nonlinearity, trapped to local optimum and high computation time, the optimization of a heat exchanger can be a robust problem. Therefore, this research introduces Univariate Search Method 2 (USM2) that can cope with such difficulties for multi-objective optimization. USM2 is based on weighted sum approach and uses a single-objective optimization method by moving from two arms on Pareto Front. To short computational time, Univariate Search Method (USM) has been chosen as a single-objective optimization method. The well-known Genetic Algorithm (GA) and Non-dominant Sorting Genetic Algorithm-2 (NSGA-2) methods were also used to compare USM and USM2 with fitness values and number of the function call corresponding to the computational time. According to the results, GA has offered better fitness values for both objectives than USM yet GA has much more number of the function call. However, USM2 has offered a better design range in the Pareto-Front than NSGA-2 despite having almost half of the function call number of NSGA-2. Moreover, the solutions offered by the USM2 at the ends of the Pareto-Front are highly competitive when compared to GA’s solutions.

Vpliv parametrov dizajna toplotnega izmenjevalnika iz polipropilenskega votlega vlakna na njegovo toplotno učinkovitost

Vpliv parametrov dizajna toplotnega izmenjevalnika iz polipropilenskega votlega vlakna na njegovo toplotno učinkovitost

Aerodynamics and Heat Transfer of Swirling Natural Gas Flow in a Vortex Heat Exchanger of the Heating System of a Gas Control Point

Purpose of research. To obtain a two-parameter model characterizing the aerodynamic and heat exchange processes occurring in a vortex heat exchanger, giving a better agreement between the calculated and experimental values of the heat transfer coefficient taking into account the curvature of the swirling gas flow in a vortex heat exchanger, in which a controlled gas pressure drop is used as a source of thermal energy. This technical solution will make it possible to abandon the installation of autonomous sources of thermal energy, which will reduce the cost of gas as a fuel in the heating system of the industrial premises of the gas distribution point (GDP), as well as provide more comfortable working conditions for the hydraulic fracturing pressure regulator. Methods. Comprehensive analysis of thermal and hydraulic characteristics in a vortex heat exchanger is based on well-known theoretical positions and equations of motion of a swirling gas flow and heat exchange laws. Results. It is obtained a dependence that characterizes the intensification of heat transfer based on the influence of the axial and rotational speed, as well as the path of motion of the swirling gas flow. This dependence is obtained on the basis of a comprehensive analysis of the aerodynamic and heat exchange characteristics of a vortex heat exchanger, in which a controlled gas pressure drop is used as a source of thermal energy. Conclusion. The obtained two-parameter model gives the best agreement of the calculated values of the heat transfer coefficient with the values obtained experimentally, which were used in the thermal engineering calculation of the design parameters of the vortex heat exchanger.

Geotechnical considerations in the design of borehole heat exchangers

The use of ground source heat pumps to transfer heat to and from the ground via borehole heat exchangers (BHEs) is among the most energy efficient techniques for space heating and cooling. Broader applications in urban environments require more careful evaluation of hydro-mechanical behavior of soil to ensure their reliable long-term performance and to minimize adverse effects on adjacent structures. An advanced soil model has been integrated within a finite difference (FD) framework, to solve coupled thermo-hydro-mechanical (THM) problems in an axisymmetric space. The FD simulator is applied to a prototype project and the ground conditions represent typical stress history profiles found in Geneva, Switzerland. An extensive parametric study is undertaken to study the long-term THM response of clay for a broad range of heat exchanger design parameters. The results show that significant settlements can be induced due to the long-term operation of BHEs (i.e., over periods from 10 to 50 years). The parametric study gives useful guidelines for heat exchanger design and identifies a design space of optimum solutions that meet pre-specified foundation settlement criteria. The study provides a qualitative investigation and a systematic framework for analyzing the long-term THM response of clay to seasonal heating and cooling.

Performance assessment of optimized heat pump water heaters using low-GWP refrigerants for high- and low-temperature applications

In this study, performance improvements of optimized heat pump water heaters (HPWHs) employing low global warming potential refrigerants are numerically evaluated against the performance of the conventional R-410A HPWH. A simulation model for HPWHs is developed and validated based on experimental results obtained in the R-410A and R-32 HPWHs. The performances of the HPWHs employing R-32, R-446A, and L-41b are simulated considering for high-temperature applications (HTAs) and low-temperature applications (LTAs) based on EN 14511. The heat exchanger design parameters of the HPWHs are optimized for achieving the maximum coefficient of performance (COP) for each alternative refrigerant. The optimized L-41b HPWH exhibits the highest COP, and the COP improvements thereof are 6.3% and 4.6% in the HTA and LTA conditions, respectively, compared with those of the R-410A HPWH. Moreover, the total equivalent warming impacts of the optimized HPWHs employing the alternative refrigerants are 5.9–9.9% lower than those of the R-410A HPWH.

RESEARCH OF THE FUNCTIONING AND OPTIMIZATION PROCESS OF THE STRUCTURAL-TECHNOLOGICAL PARAMETERS

Domestic and foreign scientists in recent years have performed a considerable amount of scientific research on the biological justification of optimal combinations of microclimate parameters required for the normal development of animals. However, the results of the studies do not allow one to specify the optimal parameters for different species of animals, taking into account their age, sex, weight and level of feeding. While it is possible to specify rather wide limits of change of temperature and relative humidity of air at which productivity is maximum, and technical and economic efficiency is approximately the same. Providing microclimate regulations in livestock premises is associated with significant costs of electricity and heat, which is about 17% of the producers' costs. To create a microclimate in livestock premises based on the above technological parameters and the analysis of the design features of the recuperators, two design and technological schemes of the three-pipe recuperator, which differ in the directions of movement of air flows, are proposed. The purpose of the research is to increase the efficiency of the technological process of functioning of the three-pipe recuperator for livestock premises by substantiating its structural and mode parameters. The results of theoretical studies of pneumatic losses in the three-pipe recuperator determined the dependence of pressure and power losses on the length of the air duct of the three-pipe recuperator, the radius of the external duct and the volume flow rate of air. As a result of theoretical studies, a mathematical model of the heat transfer process in a three-pipe heat exchanger was developed, with condensation in it, which allows to determine the temperature distribution of air flows by its length and its thermal capacity. The results of theoretical studies of the process of heat transfer in the design and technological schemes of a three-pipe recirculator with counter-current and direct-current showed that the counter-current variant is more effective. Optimization of the results of theoretical studies allowed us to determine the dependence of the design parameters of the three-pipe heat exchanger on the volumetric flow rate of air, subject to the highest useful thermal power.

Simulation of the effectiveness of longitudinal rectangular fins on the efficiency of the double pipe heat exchanger

In this article, a mathematical simulation of a double pipe heat exchanger is carried out, having the longitudinal rectangular fins with the dimension of (2*3*1000) mm, mounted on the outer surface of the inner tube of the heat exchanger. In this paper, the advantage of using of that type of fins and its effect on the effectiveness of the heat exchanger are studied with the help of the computer program. The carried out research allowsmaking the calculation to find the optimum design parameters of heat exchangers. The outer tube diameter is (34.1mm) while the inner tube diameter is (16.05mm). The tubes wall thickness is (1.5mm) and the model length was (1 m). The hot water is flowing through the inner tube in parallel with the cold water that passing the outer tube. The hot and cold water temperature at the inlet is (75°C & 30°C) respectively. The mass flow rate inside the central pipe is (0.1 kg/s) while the annular pipe carrying (0.3 kg/s). In the present work, the program ANSYS Workbench 15.0 was used to find out the results of heat transfer as well as the behavior of liquids inside the heat exchangers.

Critical comparison between thermal performance test (TPT) and thermal response test (TRT): Differences in heat transfer process and extractable information

In the field of ground-source heat pumps (GSHPs), thermal response tests (TRTs) with constant heat rate have been conducted to estimate the design parameters of ground heat exchangers (GHEs), and thermal performance tests (TPTs) with constant inlet temperature have been conducted to examine the heat exchange performance of GHEs. These two experimental methods have been discussed insufficiently, and therefore, they are sometimes perceived as completely different experiments with mutually exclusive extractable information. However, both methods provide similar information, although there are differences in the heat transfer process. For better understanding these two methods and extending the utilization potential of TPT and TRT data, this study analyzes and discusses the following two issues using numerically generated datasets: (1) differences in heat transfer process between TRTs and TPTs and (2) effect of different physical processes on the extractable information and its accuracy, such as the ground thermal conductivity, borehole thermal resistance, unit heat exchange rate, and transient ground thermal resistance. From the viewpoint of the heat transfer process, we found that the GHE’s heat storage effect disappears faster in TPT than in TRT. When estimating ground thermal properties, this difference allows the TPT to be more accurate with shorter experiment time than the TRT. Additionally, we found that the TRT overestimated the GHE thermal performance compared to the TPT. However, when the heat storage effect was removed, both methods provided almost identical results. A comparison of experimentally obtained ground thermal resistances, which are required in the ASHRAE design method, with those obtained from the infinite cylindrical source model indicated that the TPT showed discrepancy rates less than ±8% whereas the TRT showed larger discrepancy rates. In particular, when the heat storage effect is not removed, the discrepancy rate for the short-term ground thermal resistance increased by ~27%.