scholarly journals A 3-Dimensional Numerical Thermal Analysis for A Vertical Double U-Tube Ground-Coupled Heat Pump

2021 ◽  
Vol 12 (2) ◽  
pp. 12-16
Author(s):  
Ali H. Tarrad ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Ground Heat Exchanger ◽  
3 Dimensional ◽  
Ground Coupled Heat Pump ◽  
Borehole Size

The ground heat exchanger plays a major role in the thermal performance and economic optimization of the ground-coupled heat pump. The present study focuses on the effect of the borehole size and the grout and soil thermal properties on the thermal assessment of these heat exchangers. A double U-tube heat exchanger was studied numerically by the COMSOL Multiphysics 5.4 software in a 3-dimensional discretization model. The double U-tube was circuited as a parallel flow arrangement and situated in a parallel configuration (PFPD) deep in the borehole. The grout and ground thermal conductivities were selected in the range of (0.73-2.0) W/m.K and (1.24-2.8) W/m.K respectively. The results revealed that the ground thermal conductivity showed a more pronounced influence on the thermal performance of the ground heat exchanger and with less extent for the grouting one. Increasing the grout filling thermal conductivity from (0.73) W/m.K to (2.0) W/m.K at a fixed ground thermal conductivity of (2.4) W/m.K has augmented the heat transfer rate by (10) %. The heat transfer rate of the ground heat exchanger exhibited marked enhancement as much as double when the ground thermal conductivity was increased from (1.24) W/m.K to (2.8) W/m.K at fixed grout thermal conductivity range of (0.78-2.0) W/m.K. It has been verified that increasing the borehole size has a negligible effect on the ground heat exchanger thermal performance when a grout with a high thermal conductivity was utilized in the ranged of examined configurations. The steady-state numerical analysis model outcomes of the present work could be implemented for the preliminary borehole design for a ground heat exchanger.

Simulation on Ground Temperature Change of GSHP System in Severe Cold Regions

2014 ◽  
Vol 945-949 ◽  
pp. 2820-2824 ◽  
Author(s):  
Li Bai ◽  
Peng Xuan Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Temperature Change ◽  
Heat Pump ◽  
Ground Heat Exchanger ◽  
Ground Source Heat Pump ◽  
Cold Regions ◽  
Ground Source ◽  
Ground Coupled Heat Pump ◽  
Operation And Management

For the case of ground-source heat pump in severe cold regions in winter, the heat transfer situation of the ground and ground heat exchanger was dynamically simulated according to the statistics of a project in Changchun to analysis the change of the ground heat, which provided references for the initial design and operation and management of the ground-coupled heat pump in severe cold regions.

scholarly journals Analysis on Thermal Performance of Ground Heat Exchanger According to Design Type Based on Thermal Response Test

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 651 ◽  
Author(s):  
Sang Bae ◽  
Yujin Nam ◽  
Jong Choi ◽  
Kwang Lee ◽  
Jae Choi
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Thermal Resistance ◽  
Heat Pump ◽  
Thermal Performance ◽  
Thermal Response ◽  
Ground Heat Exchanger ◽  
Thermal Response Test ◽  
Borehole Thermal Resistance

A ground source heat pump (GSHP) system has higher performance than air source heat pump system due to the use of more efficient ground heat source. However, the GSHP system performance depends on ground thermal properties and groundwater conditions. There are many studies on the improvement of GSHP system by developing ground heat exchanger (GHX) and heat exchange method. Several studies have suggested methods to improve heat exchange rate for the development of GHX. However, few real-scale experimental studies have quantitatively analyzed their performance using the same ground conditions. Therefore, the objective of this study was to evaluate the thermal performance of various pipe types of GHX by the thermal response test (TRT) under the same field and test conditions. Four kinds of GHX (HDPE type, HDPE-nano type, spiral fin type, and coaxial type) were constructed in the same site. Inlet and outlet temperatures of GHXs and effective thermal conductivity were measured through the TRT. In addition, the borehole thermal resistance was calculated to comparatively analyze the correlation of the heat exchange performance with each GHX. Result of the TRT revealed that averages effective thermal conductivities of HDPE type, HDPE-nano, spiral fin type, and coaxial type GHX were 2.25 W/m·K, 2.34 W/m·K, 2.55 W/m·K, and 2.16 W/m·K, respectively. In the result, it was found that the average borehole thermal resistance can be an important factor in TRT, but the effect of increased thermal conductivity of pipe material itself was not significant.

scholarly journals Thermal Characteristics of Slinky-Coil Ground Heat Exchanger with Discrete Double Inclined Ribs

Resources ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 105
Author(s):  
Teguh Hady Ariwibowo ◽  
Akio Miyara
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Ground Heat Exchanger ◽  
Average Heat ◽  
Thermal Mixing

The slinky ground heat exchanger (GHE) is the most widely utilized horizontal-type GHE, however, this GHE has a low curvature coil. The GHE has poor thermal mixing, especially at a low flowrate. At this flowrate, the coil heat exchanger has similar performance to a straight tube heat exchanger. Discrete double-inclined ribs (DDIR) are well known for their good thermal mixing by generating a vortex in straight tubes. In this paper, a numerical analysis of thermal performance for the plain coil and DDIR coil is discussed. It was found that the thermal performance of the DDIR coil was slightly higher than that of the plain coil in laminar flow. In turbulent flow, the DDIR coil was superior to the plain coil only in the first 149-min operation. The first 60-min analysis shows that in laminar flow, the average heat transfer rate in the plain coil is 59 W/m and in the DDIR coil is 60.1 W/m. In turbulent flow, the average heat transfer rate is 62 W/m, and the plain coil is 62.3 W/m. The copper DDIR coil material produced a better heat transfer rate than that of the composite and High-Density Polyethylene (HDPE). Sandy clay has the highest heat transfer rate. The influence of ground thermal conductivity on the performance of the GHE is more dominant than convection in the DDIR coil.

Performance Evaluation of a Vertical U-Tube Ground Heat Exchanger Using a Numerical Simulation Approach

2013 ◽  
Vol 724-725 ◽  
pp. 909-915
Author(s):  
Ping Fang Hu ◽  
Zhong Yi Yu ◽  
Fei Lei ◽  
Na Zhu ◽  
Qi Ming Sun ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Transfer Process ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Ground Heat Exchanger ◽  
Ground Source Heat Pump ◽  
Ground Source

A vertical U-tube ground heat exchanger can be utilized to exchange heat with the soil in ground source heat pump systems. The outlet temperature of the working fluid through the U-tube not only accounts for heat transfer capacity of a ground heat exchanger, but also greatly affects the operational efficiency of heat pump units, which is an important characteristic parameter of heat transfer process. It is quantified by defining a thermal effectiveness coefficient. The performance evaluation is performed with a three dimensional numerical model using a finite volume technique. A dynamic simulation was conducted to analyze the thermal effectiveness as a function of soil thermal properties, backfill material properties, separation distance between the two tube legs, borehole depth and flow velocity of the working fluid. The influence of important characteristic parameters on the heat transfer performance of vertical U-tube ground heat exchangers is investigated, which may provide the references for the design of ground source heat pump systems in practice.

An Experimental Study on the Thermal Performance Evaluation of SCW Ground Heat Exchanger

2017 ◽  
Vol 25 (01) ◽  
pp. 1750006 ◽  
Author(s):  
Keun Sun Chang ◽  
Min Jun Kim ◽  
Young Jae Kim
Keyword(s):  
Thermal Conductivity ◽  
Performance Evaluation ◽  
Heat Exchanger ◽  
Effective Thermal Conductivity ◽  
Thermal Performance ◽  
Thermal Response ◽  
High Heat ◽  
Injection Rate ◽  
Operating Parameters ◽  
Ground Heat Exchanger

In recent years, application of the standing column well (SCW) ground heat exchanger (GHX) has been noticeably increased as a heat transfer mechanism of ground source heat pump (GSHP) systems with its high heat capacity and efficiency. Determination of the ground thermal properties is an important task for sizing and estimating cost of the GHX. In this study, an in situ thermal response test (TRT) is applied to the thermal performance evaluation of SCW. Two SCWs with different design configurations are installed in sequence to evaluate their effects on the thermal performance of SCW using a single borehole. A line source method is used to derive the effective thermal conductivity and borehole thermal resistance. Effects of operating parameters are also investigated including bleed, heat injection rate, flow rate and filler height. Results show that the effective thermal conductivity of top drawn SCW (Type A) is 11.7% higher than that of bottom drawn SCW (Type B) and of operating parameters tested bleed is the most significant one for the improvement of the thermal performance (40.4% enhanced in thermal conductivity with 10.9% bleed).

Prediction of Non-Uniform Frost Distribution on a Fin Tube Heat Exchanger

2013 ◽  
Author(s):  
Jieun Hwang ◽  
Keumnam Cho
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Heat Pump ◽  
Transfer Rate ◽  
Volume Flow Rate ◽  
Local Data ◽  
Tube Heat Exchanger ◽  
Side Pressure ◽  
Fin Tube

Heat exchanger experiences frost on its surface when it operates below 0°C under heating condition of the heat pump. Since frost blocks air flow through the fin tube heat exchanger, it increases air-side pressure drop and deteriorates heat transfer rate of the heat exchanger. Prediction of the frost profiles on the heat exchanger is needed to minimize the unfavorable effect on the heat exchanger by frost. The present study predicts non-uniform frost distribution on the surface of fin-tube heat exchanger and shows its accuracy by comparing with measured profiles. Fin and tube heat exchanger for heat pump was considered for the frost prediction under practical refrigerant and air conditions. Non-uniform frost pattern was predicted by using segment by segment method of the heat exchanger. Heat transfer rate and exit temperature of air and refrigerant for each segment were calculated by applying ε-NTU method. Air volume flow rate in the front of the heat exchanger was decreased as frost goes on. It was utilized for the prediction of the frost formation. Numerically predicted results were compared with measured local data. They agreed within ±10.4% under the ISO 5151 condition.

Performance Evaluation of Tube-in-Tube Heat Exchanger Using Nanofluids

2015 ◽  
Vol 787 ◽  
pp. 72-76 ◽  
Author(s):  
V. Naveen Prabhu ◽  
M. Suresh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Element Analysis ◽  
Tube Heat Exchanger

Nanofluids are fluids containing nanometer-sized particles of metals, oxides, carbides, nitrides, or nanotubes. They exhibit enhanced thermal performance when used in a heat exchanger as heat transfer fluids. Alumina (Al2O3) is the most commonly used nanoparticle due to its enhanced thermal conductivity. The work presented here, deals with numerical simulations performed in a tube-in-tube heat exchanger to study and compare flow characteristics and thermal performance of a tube-in-tube heat exchanger using water and Al2O3/water nanofluid. A local element-by-element analysis utilizing e-NTU method is employed for simulating the heat exchanger. Profiles of hot and cooling fluid temperatures, pressure drop, heat transfer rate along the length of the heat exchanger are studied. Results show that heat exchanger with nanofluid gives improved heat transfer rate when compared with water. However, the pressure drop is more, which puts a limit on the operating conditions.

An experimental work on the performance of a solar-assisted ground-coupled heat pump using a horizontal ground heat exchanger

2021 ◽  
Author(s):  
A.M. Bulmez ◽  
V. Ciofoaia ◽  
G. Năstase ◽  
G. Dragomir ◽  
A.I. Brezeanu ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Experimental Work ◽  
Ground Heat Exchanger ◽  
Ground Coupled Heat Pump
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