Possible energy saving of evaporative passive cooling using a solar chimney of metal foam porous absorber

Abstract

• Possible energy saving investigation is beneficial for reducing energy demand. • Porous absorber techniques are helpful in improving the thermal efficiency of solar chimney. • Increasing the thermal efficiency of solar chimney leads to improve the natural cooling. An experimental study has been carried out for testing the thermal performance and the thermal behavior enhancement of solar chimneys that can be achieved by adding metal foam. The solar chimney with test room system was positioned in Baghdad city, Iraq, where the solar chimney was directed to the south and situated at latitude 33.3° N, longitude 44.4° E. In the experimental part of this study, It is designed, manufactured, and tested to study the effect of some parameters that affect the performance of the solar chimney in steady-state conditions. the system has been exposed to initial tests in which the velocity, thermocouples, pressure and humidity measurements tap position is located and the rig manufacturing obstacles are evaluated and solved. The outdoor test was conducted side by side in the period from December (2020) to July (2021). The experiments were carried out from 9:00 AM to 4:00 PM for clear days. The experimental side is to test two types of copper metal foam (10 and 40) PPI as a heat absorber plate with different inclination angles (30, 45, 60, and 75) degrees and compare the performance of the metal foam absorber with that of the conventional flat absorber plate. The experimental results demonstrated that the presence of metal foam produced reducing the average temperature of absorber plate value. The highest reduction in the plate temperature was obtained experimentally with (10 and 40) PPI absorber plate (13.5 and 8.3) ℃ respectively at (Θ = 60°) compared to the conventional flat absorber plate. The maximum enhancement of the airflow velocity at the solar chimney with (10 and 40) PPI absorber plate is recorded to about (27.3% and 11.1%) respectively at Θ = 45 ͦ and to about (43.7% and 25%) respectively at Θ = 60° compared to the conventional flat absorber plate. The thermal efficiency of the chimney is increased by using metal foam as an absorber plate (10 and 40) PPI to record maximum values at 12:00 PM. The maximum mean thermal efficiency of the solar chimney that logged between the (Flat plate and metal foam 40 PPI, metal foam 10 PPI) absorber plate was 49%, 66.2%, and 72.1% respectively at an inclination angle of 60°. The maximum air change per hour in the test room that logged between the (Flat plate and metal foam 40 PPI, metal foam 10 PPI) absorber plate was (18.8 1/hr), (24.4 1/hr), and (27.2 1/hr) respectively at inclination angle 60°. In evaporative cooling mode, the greatest evaporative exit temperature difference, 4.5–7 °C, and indoor dry-bulb temperature 2.5–3.2 occurred when the maximum solar radiation. During the cooling season, the aforementioned system is capable of meeting approximately 20% of the cooling demand during the daytime.