What type of heat transfer is geothermal energy?

Geothermal energy is considered a renewable resource. Land-based heat pumps and direct-use geothermal technologies are used for heating and cooling applications, while deep and improved geothermal technologies generally take advantage of a much deeper and higher temperature geothermal resource to generate electricity. Zhang (200 years old) presented in his doctoral thesis that in conventional ground-to-air heat exchanger (ETAHE) systems, it is typical to have 10 cm underground ducts. The hydraulic diameter of a circular tube is simply the diameter of the tube.

Therefore, it is reasonable to assume that air flows are mostly developed in EAHEs of such sizes and to adapt the corresponding empirical correlations to calculate the convective heat transfer coefficient (CHTC). To examine this assumption, eight correlations with the Nusselt number (N u) were used in other ETAHE simulation studies (Arzano and Goswami 1997; Bojic et al. Since all correlations were derived for a fully developed turbulent airflow, ideally, they are expected to yield similar values for the same operating condition. The variation of the Nusselt number with respect to the Reynold number for a typical conventional ETAHE design was calculated using the eight correlations to calculate the CHTC, and very large differences were observed between the results of the eight correlations.

This may be due to different experimental conditions, which were adopted to derive the correlations, for example, the surface roughness of the experimental ducts. The large discrepancies indicate that an appropriate correlation should be selected if any of the existing models are used to simulate the performance of an EAHE system. . Assuming that the inner surface of the PVC pipes used in the EAHE system is smooth, the N u correlations provided by De and Janssens (200) can be used to simulate system performance.

Arzano L, Goswami DY (1999) Analysis of the performance of a closed-loop underground air tunnel for residential homes in a hot and humid climate. Proceedings of the ISES World Solar Congress, Taejon (South Korea), August 1997: Benkert S, Heidt FD, Scholer D (199) Calculation tool for GAEA terrestrial heat exchangers. Building Simulation Proceedings, 5th IBPSA International Conference, Prague, Czech Republic, pp. September 9, 1997, 5 Department of Mechanical Engineering, Sagar Research Institute,% 26 technological excellence, Bhopal, 462041, India.

For example, a heat pump with a COP of 3 provides 3 kWh (kilowatt hours) of heat for every 1 kWh of electricity consumed. The EAHE performance analysis involved calculating heat transfer by conduction from pipe to soil mass or calculating convective heat transfer from circulating air to the pipe and changes in air temperature and humidity. Geothermal energy, the thermal energy of the Earth's interior, is used to generate electricity in a variety of places around the world. GHP takes advantage of these more favorable temperatures to be highly efficient at exchanging heat with the earth through a terrestrial heat exchanger.

Ozgener O, Ozgener L, Teste JW (201) A practical approach to predicting soil temperature variations for geothermal (terrestrial) heat exchanger applications. A heat pump is a device for transferring a certain amount of heat from a first medium, called an emitter, to another medium, called a receiver. Geothermal energy, a form of energy conversion in which thermal energy from the Earth's interior is captured and used for cooking, bathing, heating spaces, generating electrical energy and other uses. Dual-source heat pumps have higher efficiency rates than air source units, but they are not as efficient as geothermal units.

While the price of installing a geothermal system may be several times greater than that of an air supply system with the same heating and cooling capacity, the additional costs can return in energy savings over 5 to 10 years, depending on the cost of energy and incentives available in your area. Luciu RS, Mateescu T, Cotorobai V, Mare T (200), Nusselt number and convective heat transfer coefficient for a coaxial heat exchanger using Al2O3 —water, pH %3D 5 nanofluid. Most closed-loop geothermal heat pumps circulate an antifreeze solution through a closed circuit, usually made of high-density plastic tubing, that is buried in the ground or submerged in water. The exploitation of conventional geothermal energy only affects natural aquifers and consists of extracting the heat contained in the aquifer by bringing its water to the surface of the soil at a temperature close to that of the aquifer.

In addition to the above-mentioned mass heat, the latent heat associated with changes in the liquid-vapor phase transition must be taken into account. Geothermal thermal energy can be recovered and exploited for human use, and is available anywhere on the Earth's surface. It is this low temperature stability that allows the installation of so-called geothermal heat pumps, as explained below. .

Aria Lavoie
Aria Lavoie

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