A comprehensive performance analysis of an EAHE could supply great help for the design and application of EAHE in gas turbine. At first the soil temperature at different depth along the year was evaluated to determine the optimum depth for high performance and low economical cost. Then the effect of structural factors including the pipe length and inner diameter, in addition the effect of air velocity passing through the pipe on the performance were studied. The air temperature at the inlet of EAHE was selected fixed at 40 ℃. It is fixed at this value because the average maximum temperature for the selected rejoin is about 40 ℃. The pipe of heat exchanger is in PVC and its thickness is 5 mm. The physical and thermal properties of air, pipe
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It is observed that the temperature of top layer of the ground at a profundity somewhere around 1 and 2 m is significantly affected with the surface temperature then this impact diminishes with increasing the ground depth. On another hand the ground temperature at a depth of 4–5 m is verging on consistent at 24 °C consistently, which it is lower than the surface temperature in summer months, consequently it is proper for summer cooling.
The temperature appropriation of the ground around the pipe is gotten to determine the thickness of the disturbed soil at different inlet temperature utilizing Eq (2.4). As appeared in Fig. 5.2 the temperature diminishing with expanding the radius of the soil surrounding the buried pipes until it reaches to the initial temperature of the ground at range of 0.5 m from the pipe surface following 12 h proceeds with operation at the three inlet temperature. The outcomes in light of considering the temperature of the pipe surface stay steady at the inlet temperatures during the …show more content…
5.4 increasing the pipe diameter leads to increasing the outlet temperature. The results shows up at the same length of 85 m, velocity of 4.5 m/s and air temperature of 40 °C, the outlet air temperature is diminished by 14.6 °C at pipe diameter of 20 cm yet it is decreased by 6.7 °C at estimation of 60cm . This is due to the fact that an increasing of pipe diameter leads to reducing the convective heat transfer coefficient at inward surface of the pipe. In addition, with increasing the diameter, the mass flow rate increases that ascent the thermal inertia of air accordingly the heat exchange between the streaming air and soil to some degree diminished. However, smaller diameter gives better thermal performance; the pressure drop is raised by 25 % as a result of diminishing the diameter from 40 to 30
It is observed that the temperature of top layer of the ground at a profundity somewhere around 1 and 2 m is significantly affected with the surface temperature then this impact diminishes with increasing the ground depth. On another hand the ground temperature at a depth of 4–5 m is verging on consistent at 24 °C consistently, which it is lower than the surface temperature in summer months, consequently it is proper for summer cooling.
The temperature appropriation of the ground around the pipe is gotten to determine the thickness of the disturbed soil at different inlet temperature utilizing Eq (2.4). As appeared in Fig. 5.2 the temperature diminishing with expanding the radius of the soil surrounding the buried pipes until it reaches to the initial temperature of the ground at range of 0.5 m from the pipe surface following 12 h proceeds with operation at the three inlet temperature. The outcomes in light of considering the temperature of the pipe surface stay steady at the inlet temperatures during the …show more content…
5.4 increasing the pipe diameter leads to increasing the outlet temperature. The results shows up at the same length of 85 m, velocity of 4.5 m/s and air temperature of 40 °C, the outlet air temperature is diminished by 14.6 °C at pipe diameter of 20 cm yet it is decreased by 6.7 °C at estimation of 60cm . This is due to the fact that an increasing of pipe diameter leads to reducing the convective heat transfer coefficient at inward surface of the pipe. In addition, with increasing the diameter, the mass flow rate increases that ascent the thermal inertia of air accordingly the heat exchange between the streaming air and soil to some degree diminished. However, smaller diameter gives better thermal performance; the pressure drop is raised by 25 % as a result of diminishing the diameter from 40 to 30