Long-term heat transfer analysis of deep coaxial borehole heat exchangers via an improved analytical model

Thermoacoustic engines and refrigerators use the interaction between heat and sound to produce acoustic energy or to transport thermal energy. Heat leaks in thermal buffer tubes and pulse tubes, components in thermoacoustic devices that separate heat exchangers at different temperatures, reduce the efficiency of these systems. At high acoustic amplitudes, Rayleigh mass streaming can become the dominat means for undesirable heat leak. Gravity affects the streaming flow patterns and influences streaming-induced heat convection. A simplified analytical model is constructed that shows gravity can reduce the streaming heat leak dramatically.

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A computationally efficient numerical model for heat transfer simulation of deep borehole heat exchangers

Energy and Buildings ◽

10.1016/j.enbuild.2018.02.013 ◽

2018 ◽

Vol 167 ◽

pp. 79-88 ◽

Cited By ~ 36

Author(s):

Liang Fang ◽

Nairen Diao ◽

Zhukun Shao ◽

Ke Zhu ◽

Zhaohong Fang

Keyword(s):

Heat Transfer ◽

Numerical Model ◽

Heat Exchangers ◽

Deep Borehole ◽

Computationally Efficient ◽

Heat Transfer Simulation ◽

Borehole Heat Exchangers

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Finite element modeling of geothermal source of heat pump in long-term operation

E3S Web of Conferences ◽

10.1051/e3sconf/202015404003 ◽

2020 ◽

Vol 154 ◽

pp. 04003

Author(s):

Elżbieta Hałaj

Keyword(s):

Finite Element ◽

Heat Source ◽

Heat Pump ◽

Heat Exchangers ◽

Transport Model ◽

Heat Pumps ◽

Initial Temperature Distribution ◽

Term Operation ◽

Borehole Heat Exchangers

Heat pumps become more and more popular heat source. They can be an alternative choice for obsolete coal fired boilers which are emissive and not ecological. During heat pump installation designing process, especially for heat pumps with higher heating capacity (for example those suppling larger buildings), a simulation of heat balance of ground heat source must be provided. A 3D heat transport model and groundwater flow in the geothermal heat source for heat pump (GSHP) installation was developed in FEFLOW according to Finite Element Modelling Method. The model consists of 25 borehole heat exchangers, arranged with spacing recommended by heat pump branch guidelines. The model consists of both a homogeneous, non-layered domain and a layered domain, which reflected differences in thermal properties of the ground and hydrogeological factors. The initial temperature distribution in the ground was simulating according to conditions typical for Europe in steady state heat flow. Optimal mesh refinement for nodes around borehole heat exchangers were calculated according to Nillert method. The aim of this work is to present influence of geological, hydrogeological factors and borehole arrangement in the energy balance and long term sustainability of the ground source. The thermal changes in the subsurface have been determined for a long term operation (30 years of operation period). Some thermal energy storage applications have also been considered.

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Heat Transfer Analysis of Shell-and-Helical-Coil Heat Exchangers

Volume 8: Heat Transfer and Thermal Engineering ◽

10.1115/imece2016-68173 ◽

2016 ◽

Author(s):

Anthony Edward Morris ◽

C. S. Wei ◽

Runar Unnthorsson ◽

Robert Dell

Keyword(s):

Heat Transfer ◽

Heat Transfer Rate ◽

Heat Exchangers ◽

Transfer Rate ◽

Green Roofs ◽

Heat Transfer Analysis ◽

Helical Coil ◽

Straight Tube ◽

Science And Art ◽

Coil Heat

Since 2006, The Center for Innovation and Applied Technology (CIAT) at Cooper Union for the Advancement of Science and Art has been developing a system to use thermal pollution to heat the growth medium of green roofs. CIAT is researching various apparatus and techniques, including shell-and-tube and shell-and-coil heat exchangers, to improve its heated ground agricultural projects. There are limited recorded observations on shell-and-coil heat exchangers; therefore a laboratory work station was created of interchangeable components to test the efficiency of a variety of coil designs. This paper discusses the data collected on temperature, pressure, and flow rates for a straight tube and two different helical coils. The analysis of this data indicates the superiority of a helical coil design when compared to a straight tube design with respect to both rating and heat transfer rate. The same data analysis has lead to preliminary observations on how the contour properties of a helical coil influence the heat transfer rate through a coil. The authors intend to further this helical coil research to develop a useful mathematical model for determining efficient designs for shell-and-coil heat exchangers.

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