scholarly journals Simplified two-step, cross-sectional approach for coupled heat and moisture transfer modeling of shallow, horizontal, ground-based heat Exchangers

2020 ◽  
Vol 205 ◽  
pp. 07004
Author(s):  
Hyunjun Oh ◽  
James M. Tinjum
Keyword(s):  
Heat Exchangers ◽  
Moisture Transfer ◽  
Environmental Control ◽  
Meteorological Data ◽  
Fluid Temperature ◽  
Heat And Moisture Transfer ◽  
Cross Sectional ◽  
Ambient Temperatures ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture

This study evaluates a two-step, cross-sectional approach for designing shallow, unsaturated, horizontal, ground-based heat exchangers (GHXs). Numerical modeling was conducted for coupled heat and moisture transfer around GHXs under transient climatological conditions through a cooling season. Soil samples were collected in Texas and Wisconsin to measure thermal conductivity dry-out curves and soil-water characteristic curves for use in the modeling. Average daily meteorological data from central Texas was applied for the top boundary condition. Heat generation from the GHX was calculated by total condenser heat rejection from an environmental control unit based on ambient temperatures and unit specifications. In the first step of the modeling, results showed that the fluid temperature through the GHX loop was approximately 43 ºC, and rapid heat and moisture fluxes were observed around the GHX loops. High moisture flux along the upper surface was also observed due to high ambient temperatures that occur during the summer season. Using these results, exiting temperature of the GHX was estimated for the second cross-sectional modeling step. This two-step, cross-sectional modeling approach provides a systematic analysis of coupled heat and moisture transfer around shallow, horizontal, unsaturated GHX loops, thus simplifying high computational effort needed for full three-dimensional modeling of shallow GHX systems.

scholarly journals Modeling of shallow, horizontal, unsaturated, ground-based heat exchangers with consideration of dry zone formation

2020 ◽  
Vol 205 ◽  
pp. 07005
Author(s):  
Hyunjun Oh ◽  
James M. Tinjum
Keyword(s):  
Thermal Properties ◽  
Heat Exchangers ◽  
Moisture Transfer ◽  
Heat And Moisture Transfer ◽  
Zone Formation ◽  
Finite Element Software ◽  
Dry Zone ◽  
High Fluid ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture

High fluid temperatures in ground-based heat exchangers (GHXs) during the cooling season may result in a decrease in thermal conductivity of adjacent backfill (λbackfill), potentially causing degradation in the performance efficiency of the GHX system. In this study, numerical modeling was performed using the SVOffice™ finite-element software to evaluate coupled heat and moisture transfer around two GHXs. Constant-temperature boundary conditions of 35 ºC were applied to the GHX surfaces, and thermal properties of the backfill were controlled for comparisons. For estimate typical hydraulic and thermal properties for the modeling, laboratory tests and literature review were performed. Modeling results indicate that coupled heat and moisture transfer occurs rapidly near the GHX involving a dry zone formation when λbackfill decreases. A boundary between dry and wet zones where soil thermal properties rapidly change was observed around 50% GHX temperature dissipated (T50), and accordingly T50 was used to optimize the pipe configuration. Coupled heat and moisture transfer increased when the GHX configurations were optimized with consideration of dry zone formation. These results imply that thermally enhanced, engineered backfill and optimized configurations can enhance GHX system efficiency.

Development of a numerical approach to assess the effect of coupled heat and moisture transfer on energy consumption of residential buildings in Moroccan context

2021 ◽  
pp. 174425912110560
Author(s):  
Yassine Chbani Idrissi ◽  
Rafik Belarbi ◽  
Mohammed Yacine Ferroukhi ◽  
M’barek Feddaoui ◽  
Driss Agliz
Keyword(s):  
Energy Consumption ◽  
Building Materials ◽  
Moisture Transfer ◽  
Residential Buildings ◽  
Building Design ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Heat And Moisture Transfer ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture

Hygrothermal properties of building materials, climatic conditions and energy performance are interrelated and have to be considered simultaneously as part of an optimised building design. In this paper, a new approach to evaluate the energy consumption of residential buildings in Morocco is presented. This approach is based on the effect of coupled heat and moisture transfer in typical residential buildings and on their responses to the varied climatic conditions encountered in the country. This approach allows us to evaluate with better accuracy the response of building energy performance and the indoor comfort of building occupants. Annual energy consumption, cooling and heating energy requirements were estimated considering the six climatic zones of Morocco. Based on the results, terms related to coupled heat and moisture transfer can effectively correct the existing energy consumption calculations of the six zones of Morocco, which currently do not consider energy consumption due to coupled heat and moisture transfer.

Ground-Coupled Heat and Moisture Transfer From Buildings: Part 1 — Analysis and Modeling

2001 ◽  
Author(s):  
Michael P. Deru ◽  
Allan T. Kirkpatrick
Keyword(s):  
Moisture Transfer ◽  
Transfer Model ◽  
Heat And Moisture Transfer ◽  
Ground Temperatures ◽  
Heat Effects ◽  
Tightly Coupled ◽  
Finite Element Procedure ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture ◽  
Properties Of Soil

Abstract Ground-heat transfer is tightly coupled with soil-moisture transfer. The coupling is threefold: heat is transferred by thermal conduction and by moisture transfer; the thermal properties of soil are strong functions of the moisture content; and moisture phase change includes latent heat effects and changes in thermal and hydraulic properties. A heat and moisture transfer model was developed to study the ground-coupled heat and moisture transfer from buildings. The model also includes detailed considerations of the atmospheric boundary conditions, including precipitation. Solutions for the soil temperature distribution are obtained using a finite element procedure. The model compared well with the seasonal variation of measured ground temperatures.

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