Literature Review on Ground Source Heat Pump and Earth-Air Heat Exchanger Systems

This literature review discusses the thermal performance of Ground Source Heat Pump (GSHP) and Earth-Air Heat Exchanger (EAHE) systems under different weather conditions. It covers the impact of global climate change on GSHP systems, the efficiency of DX-GCHP system during different seasons, and the effect of pipe diameter and length on air temperature in EAHE systems. The review also includes a discussion on the design and productivity of horizontal and vertical GCHP systems.

LITERATURE REVIEW
In the research conducted by Kharseh et al. (2015) it is depicted that a Ground Source Heat
Pump (GSHP) system may be used for the heating and cooling of buildings. In the winter season,
the GSHP system transfers the heat from the ground to the buildings, and during the summer, the
heat is transferred from the buildings to the ground. Two buildings that are constructed in three
cities with three different climates and these were taken as references. One building was
Stockholm in Sweden in a cold season, the second was in Doha, Qatar in a hot climate, and the
third city was in Istanbul, Turkey in the mild season. In general, a building has a lifespan of
about 50 years or more. In the study, the weather information in 2014 was used and the data for
2050 was predicted using the Meteonorm software. Moreover, by the year of 2050, the mean
temperature will increase in each city and the temperature rise around 1.3 °C in Stockholm, 0.9
°C in Doha, and 1.8 °C in Istanbul (Soni et al. 2016).
Likewise , research was conducted by Serageldin et al. (2016) on the heat exchange of the air in
Egypt. In the study, an Earth-Air Heat Exchanger (EAHE) system was used to heating and
cooling purposes. The thermal performance of this system was studied under Egyptian weather
conditions. The MATLAB code was applied to seek solutions to the developed heat transfer
equation. The pipes used in the experiment were studied carefully and it was noticed that as the
diameter of a pipe increases the air temperature reduces. Simultaneously, as the length of the
pipe increases, the air temperature increases. Compared to the air passing through copper and
steel pipes, the air temperature is less when passing through PVC pipes. The reason is that PVC
pipes have a high thermal resistance whereas copper and steel pipes both have a low thermal
resistance. The air temperature in the PVC pipes were 19.7 °C, and in the copper and steel and
pipes etc was 19.8 and 19.7 respectively (Serageldin et al., 2016). Therefore, it was observed that
when the fluid velocity in the pipes increases, the outlet air temperature gradually decreases.
On the other hand, Soni et al. (2016) have studied the heat exchange system. The authors state
that the Ground Coupled Heat Exchanger (GCHE) system is an energy efficient technology for
both space heating and cooling purposes. As the infrastructures increase, the demand for energy
supply also increases for the need of space heating and cooling. With this problem, the use of
GCHE systems is also gaining popularity with the DX-GCHP system, a type of GCHE system
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being experimented on harsh conditions. However, the use of the system that are employed in
locations that are used in the experiment. The experiments were carried out for the summer and
rainy season in Bhopal, India. It was observed that the energy consumption reduced during the
rainy season and increased during the summer. During the monsoons, the energy was reduced
about 11.25% in a horizontal configuration and 14.68% in a vertical configuration. Also in the
summer season, the energy increased by about 3.12% in the horizontal and 3.41% in vertical
configurations (Soni et al., 2016). Henceforth, the experimental outcomes claim that the DX-
GCHP system is more efficient during the rainy season than in the summer season.
In the paper of Said et al. (2005) Ground-CoupledHeat Pumps (GCHP) systems are divided into
three GHE designs and these are, horizontal, vertical and slinky. The horizontal configuration of
the GCHP system requires a larger ground zone and this contrast with the vertical GCHP system
and the horizontal system has the lower productivity. However, the horizontal GCHPs are
usually more affordable. A heat exchange technique is utilised to display that the horizontal
ground heat exchanger and an intuitive product program is created. The program has the capacity
of predicting the required surface zone and like this the conceptual design of the horizontal
ground heat exchanger required for a GHP of a given cooling limit and given COP. The
experimental outcomes show that the differences in the ground temperature starting in one area
then onto the next has a noteworthy impact on the length of the general pipe (Said et al., 2005).
When the overall length of the pipe increases because of the increase in the head loss, then the
power of the pump also increases. Consequently, the pump power decreases when the number of
parallel loops increases.
In the study carried out by Belatrache et al. (2017), it is depicted that the Earth Air Heat
Exchangers (EAHE) are comprised of one or more pipes that are placed underground for the
heating and cooling purposes in buildings. The modelling and simulation methods were
advanced to comprehend the thermal performance of this system. The earth air heat exchanger
contains primarily a PVC pipe of length 45m. The EAHE was at the depth of 5 m in the Algerian
Sahara. A parametric examination was accomplished to assess and research the impact of the
covered length of the pipe and the wind current rate on the air temperature at the tube exit. Upon
evaluation, it was observed that the air temperature decreases until it becomes equal to the
temperature of the soil along with the 25m pipe length. In July, the air temperature diminishes
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from the most extreme surrounding temperature of 46 °C until it achieves the soil temperature at
about 25 °C (Belatrache et al., 2017).
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REFERENCES
Belatrache, D., Bentouba, S. & Bourouis, M. (2017) Numerical analysis of earth air heat
exchangers at operating conditions in arid climates. International Journal of Hydrogen
Energy, 42 (13), pp.8898–8904.
Kharseh, M., Altorkmany, L., Al-Khawaja, M. & Hassani, F. (2015) Analysis of the effect of
global climate change on ground source heat pump systems in different climate categories.
Renewable Energy, 78, pp.219–225.
Said, S. a M., Habib, M. a, Mokheimer, E.M. a & Sharqawi, M. (2005) Horizontal Ground Heat
Exchanger Design for Ground-Coupled Heat Pumps. , (August 2015).
Serageldin, A.A., Abdelrahman, A.K. & Ookawara, S. (2016) Earth-Air Heat Exchanger thermal
performance in Egyptian conditions: Experimental results, mathematical model, and
Computational Fluid Dynamics simulation. Energy Conversion and Management, 122,
pp.25–38.
Soni, S.K., Pandey, M. & Bartaria, V.N. (2016) Experimental analysis of a direct expansion
ground coupled heat exchange system for space cooling requirements. Energy and
Buildings, 119, pp.85–92.
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