Rohit Misra

Evaluating Thermal Performance and Energy Conservation Potential of Hybrid Earth Air Tunnel Heat Exchanger in Hot and Dry Climate—In Situ Measurement

Earth air tunnel heat exchanger is a passive cooling device with advantageous feature to reduce energy consumption in buildings. Curtailing the electricity consumption of conventional vapor compression system based air-conditioner is a major concern especially in area with hot and dry weather conditions. The performance of conventional air-conditioners can substantially be enhanced by coupling these active cooling systems with passive cooling systems. In the present research, the thermal performance and energy conservation potential of hybrid cooling system has been investigated experimentally. An attempt has been made to enhance the thermal performance of active cooling system by coupling it with earth air tunnel heat exchanger (EATHE) in two different hybrid modes. The air which comes out of EATHE is relatively cooler than the ambient air and therefore can be used either for cooling the condenser tubes of a conventional window type air-conditioner or supplying it directly to the room being conditioned. The energy consumption of conventional 1.5TR window type air conditioner is found to be reduced by 16.11% when cold air from EATHE is completely used for condenser cooling.

Thermal performance enhancement of box-type solar cooker: a new approach

A comparative experimental study of two box-type solar cookers with different cooking environments was conducted. The first one with natural convection heat transfer-based and the second one with forced convection heat transfer (fan for flow augmentation)-based environment. The experimental results show that the forced convection-based environment remarkably improves the thermal performance of box-type solar cooker. Forced convection-based cooker is able to cook food at much faster rates compared with natural convection-based cooker. This reduces the cooking time considerably. Results of thermal performance tests show (i) stagnation absorber plate temperatures of 133.9°C and 119.3°C and (ii) boiling times of 52 min (3120 s) and 75 min (4500 s) for heating 1 kg of water, for the cooker with and without fan, respectively. The solar cooker performance has been rated using the first figure of merit (F1) on the no-load test and the second figure of merit (F2) on the sensible heat tests. The cooking time was considerably reduced by 30.6%. The tests were carried out on the research unit in Government Engineering College Ajmer, Rajasthan located at 26°27′ N latitude and 74°42′ E longitude in India.

Optimization of operating parameters of earth air tunnel heat exchanger for space cooling: Taguchi method approach

In the present study, CFD-based parametric analysis is carried out to optimise the parameters affecting the temperature drop and heat transfer rate achieved from earth air tunnel heat exchanger (EATHE) system. ANSYS FLUENT 15.0 is used for CFD analysis, and k-ε model and energy equation were considered to define the turbulence and heat transfer phenomena. For a straight EATHE system configuration, four design and operating parameters, i.e., diameter of the pipe (A), length of pipe (B), inlet air velocity (C), and inlet air temperature (D), are considered at four different levels in Taguchi method. The Taguchi method is used to obtain maximum air temperature drop and heat transfer rate. The best combination of parameters for achieving a maximum drop in air temperature is A1B4C1D4 and that for obtaining maximum total heat transfer rate is A4B4C4D4. Statistical analysis reveals the percentage contribution of different factors for air temperature drop in the following order: inlet air temperature (57.80%), diameter of pipe (20.66%), length of pipe (12.03%), and air velocity (9.51%), while, for heat transfer rate, pipe diameter (53.28%), inlet air temperature (30.87%), air velocity (9.40%), and length of pipe (6.45%).