Coupling Thermal Conductivity Dry-Out Curves with Unsaturated Soil Modeling of Shallow Horizontal Geothermal Exchange Loops

2014 ◽  
Author(s):  
Ray Wu ◽  
James M. Tinjum ◽  
William J. Likos
Keyword(s):  
Thermal Conductivity ◽  
Unsaturated Soil ◽  
Dry Out

The Primary and Secondary Analysis of Uncertain Factors in Soil Thermal Properties for GSHP

2012 ◽  
Vol 614-615 ◽  
pp. 688-694 ◽  
Author(s):  
Yi Wang ◽  
Guo Min Shen
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Water Table ◽  
Unsaturated Soil ◽  
Solid Phase ◽  
Saturated Soil ◽  
Soil Thermal Conductivity ◽  
Saturation Degree ◽  
Soil Thermal Properties ◽  
Soil Solid Phase

In this paper, at first, an effective soil thermal conductivity model was established. Single factor regression analysis for 6 uncertain factors contained in the model was then conducted respectively. Finally, the primary and secondary characters of these uncertain factors were analyzed by using the orthogonal test. The analysis results show that the effective soil thermal conductivity has linear relationships with the saturation degree of unsaturated soil and the depth of water table and has power function relationships with other 4 uncertain factors; the porosity of unsaturated soil has the greatest effect on the effective soil thermal properties, followed by saturation degree of unsaturated soil, porosity of saturated soil, solid phase thermal conductivity of unsaturated soil, solid phase thermal conductivity of saturated soil and the depth of water table.

scholarly journals Thermal properties of a tropical unsaturated soil

2021 ◽  
Vol 337 ◽  
pp. 01019
Author(s):  
Thaise da Silva Oliveira Morais ◽  
Cristina de Hollanda Cavalcanti Tsuha ◽  
Orencio Monje Vilar
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Thermal Characteristics ◽  
Thermal Response ◽  
Test Site ◽  
Degree Of Saturation ◽  
Ambient Temperatures ◽  
Heating And Cooling

Ground thermal properties, especially the thermal conductivity, are of paramount importance for the design of ground source heat pump systems (GSHP), used for space heating and cooling. However, very little information, if any, are available from the thermal characteristics of tropical unsaturated soils related to the GSHP application. To evaluate the thermal behaviour of a typical Brazilian tropical unsaturated soil, an extensive experimental investigation was conducted at the test site of the University of Sao Paulo at São EESC/USP) comprising Carlos (a detailed soil characterization; field monitoring of the seasonal groundwater table variation; soil and ambient temperatures, and matric suction of the top soil. This paper describes the investigation program and compares the thermal soil properties as measured in laboratory and field thermal response tests. The results were variable depending on the testing techniques; however, all results showed that the soil thermal conductivity is strongly influenced by the degree of saturation of the soil.

scholarly journals Performance and impact of cryogenic pulsating heat pipe using a different number of turns and helium gas

2021 ◽  
pp. 210-210
Author(s):  
Arunkumar Munimathan ◽  
Mohanavel Vinayagam ◽  
Prabhu Rajalingam ◽  
Ganesamoorthy Raju ◽  
Suban Kaveripakkam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Pipe ◽  
High Capacity ◽  
Temperature Response ◽  
Heat Transfer Process ◽  
Pulsating Heat Pipe ◽  
Long Distance ◽  
Transfer Capability ◽  
Dry Out

The present work involves the development of helium based Pulsating heat pipe (PHP), which containing 48 parallel tubing parts. Pulsating heat pipe (PHP) is considered as one of the best alternatives for conducting metals and it is used for long distance heat transfer process. Their heat transfer capability and efficient thermal conductivity are the prominent properties which considered for applications. The region of the condenser was thermally sealed to the giffored mcmohanon cryo-cooler [gm-cryo cooler] using a cooling cap of 1.49 W at 4.2 K while 1.1 W of heat are allowed to the evaporator section at a filling rate of 70%, through comparing the 48-turn PHP and 8-turn PHP, a most intense efficient thermal conductivity of 12329 W/ mK was achieved in the 48 turn PHP. The influence of no turns of warm movement execution was observed with the same operating parameters and topographical parameters. Observations revealed that the temperature variations of PHP 48-turn was significantly less than that of PHP 8-turn. It exhibited efficient thermal conductivity, high capacity heat transfer and a good dry-out temperature response. Thus PHP 48-turn of series and parallel configurations are defined as excellent system designs and are accessible to the PHP cryogenics framework architecture.

Modeling Transient Heat Transfer and Dry-Out Phenomena in Heat Pipes Using Finite Element Analysis

2020 ◽  
Author(s):  
Mustafa Özçatalbaş ◽  
Ramazan Aykut Sezmen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Finite Element ◽  
Heat Pipe ◽  
Heat Removal ◽  
Heat Pipes ◽  
Heat Transfer Analysis ◽  
Transient Heat Transfer ◽  
Dry Out

Abstract Heat pipes are passive two-phase heat transfer devices that used in various heat transport applications because of their high thermal conductance capacities with low temperature differences. One of these applications is aerospace avionics that heat pipes are exposed to transient heat loads. Although heat pipes have been one of the heat removal alternatives for compact electronic devices, they have some restrictions during the usage in such high heat flux areas. In order to use heat pipes as effective heat removal devices, operating heat load range should not be exceeded during the operation of avionics or electronic devices. Out of these operating range, heat pipes no longer perform as effective heat removal devices because of phenomena called dry-out. In this study, a novel Finite Element (FE) Analysis Method was developed to model transient heat transfer behavior in heat pipes including dry-out phenomenon. Transient heat transfer analysis using Finite Element Method (FEM) was conducted to investigate heat pipe thermal performance considering heat flux dependent thermal conductivity under randomly varying heat inputs, which were assumed as heat dissipation of an electronic device. Validation of the FE model was done by using the results given in the literature. Heat pipe was made of Al with a length of LHP = 200 mm. Heat flux and convective heat transfer boundary conditions were used at the evaporator and condenser sections, respectively. Effective thermal conductivity of heat pipe, keff, was calculated by using the heat input depended thermal resistance, Rth, values given in literature. Under transient heat loads, heat flux dependent effective thermal conductivity was defined using user defined subroutines to simulate the dry-out. The transient heat transfer analysis was conducted using ABAQUS commercially available software. Temperature differences between evaporator and condenser sections, ΔT = Te−Tc, and thermal resistance, Rth, values are calculated for varying heat input values and compared with the results that provided in literature.

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