No abstract

No abstract

In a jet impingement cooling (JIC) system, the layout of the target surface and length of the jet holes can change both the flow field and the heat transfer characteristics. Elliptical-shaped pins (ESPs) with different heights and layouts on the target surface of the extended jet hole configurations were examined numerically in a jet impingement system. Normalized nozzle length (Gj/Dj) and normalized pin height (Hp/Dj) were investigated as geometric parameters. Also, the effect of different pin layouts (R1, R2, R3) on heat transfer dissipation was studied by changing the number of pin rows in particular configurations. Numerical analyses were conducted under turbulent flow conditions (16250 ≤ Re ≤ 32500). Nusselt (Nu) numbers, pressure drop, and the thermo-hydraulic performance of the physical model were quantitatively researched to elucidate the underlying mechanisms of enhanced heat transfer by the ESPs. Results showed that area-averaged Nu number on the target wall increased up to 35.82% for Re = 16250 by R2Gj/Dj = 1.0 and Hp/Dj = 0.167 compared to the conventional JIC system. The performance evaluation criterion (PEC) was used to analyze the thermo-hydraulic performance of the examined physical models. According to the PEC values, the most feasible parameters for all Re numbers were R3Gj/Dj = 1.0 and Hp/Dj = 0.167. Furthermore, increasing the number of pin rows in the channel also increased the uniformity of the local heat transfer distribution according to Nu contours.

No abstract

The energy crises that emerged after the economic problems in the world increased the interest in alternative energy resources. The effects of global warming, which has a serious threat, will be reduced by the more efficient use of these energy resources. In this study, the thermal effects of wet soil were investigated experimentally using a ground source heat exchanger (GHE), which is an alternative energy resource, in an area on the Esentepe campus of Sakarya University. Researches on this subject are mostly directed to dry soil applications. In this study, the thermal performance of GHE was examined in terms of heat transfer. By means of the artificial pool formed under the ground, it is aimed to increase in heat transfer between the soil and the process fluid. In the experiments which are conducted, air is used as the process fluid. The system has a significant advantage in certain temperature ranges due to the passive heating method, in other words, the process fluid can be circulated under the soil without using a compressor. The purpose of this method is to reduce the cost of heating in the winter season. The temperature difference at GHE inlet and outlet is approximately 9.07 °C in the experiments. The heat transfer rate has been increased by 46.28% compared to dry soil application for the same air velocity speed.