Passive cooling of buildings by using integrated earth to air heat exchanger and solar chimney

This is the property of earth that at a depth of about 1.5 to 2 m, the temperature of ground remains almost constant throughout the year. This constant temperature is called earth’s undisturbed temperature which remains higher than surface temperature of earth in winter season and vice versa in summer. For effective utilization of heat capacity of earth, the earth–air heat exchanger (EAHE) has to be designed. The EAHEs are considered as an effective passive heating/cooling medium for buildings. This is basically a series of metallic, plastic or concrete pipes buried underground at a particular depth through which the fresh atmospheric air flows and gets heated in winter and supplied to the building if at sufficiently high temperature and vice versa in summer. Till date many researchers have carried out a number of studies in designing, modeling and testing of EAHEs systems. This paper reviews on the experimental and analytical studies of EAHE systems around the world but the studies are mainly focused on EAHE systems at the Indian universities as of the end June, 2012.

Experimental and analytical studies of earth–air heat exchanger (EAHE) systems in India: A review

During the last three decades, a number of studies have been conducted by various investigators in the design, modeling and testing of earth to air heat exchanger (EAHE) systems. This paper reviews the studies conducted on the experimental and analytical analysis of EAHE systems in Turkey and around the world as of the end February 2011. The studies undertaken on the EAHE systems are categorized into two groups as follows: (i) open loop for space heating/cooling and (ii) closed loop for space heating/cooling systems. This paper investigates the studies on EAHEs, also known underground air tunnel systems.

A review on the experimental and analytical analysis of earth to air heat exchanger (EAHE) systems in Turkey

Passive cooling in a low-energy office building

Techno-economic assessment and optimization of a hybrid renewable earth - air heat exchanger coupled with electric boiler, hydrogen, wind and PV configurations

This paper presents heat transfer analysis of a passive summer cooling and winter preheating technique, which utilizes the underground temperature at a depth of 6 ft (1.83m) or more. In this study, a computer model solution has been developed for predicting the air temperature at any point, at any time while passing through the underground pipe. The air temperature is a function of the inlet air temperature and humidity, soil temperature, soil properties, the pipe (length, diameter, shape, and material), and the air flow velocity. Experiments were performed to measure air temperature, soil temperature, and pipe surface temperature at different lengths and different intervals of times. The results of the experiments are compared with theoretical calculations, which showed very good agreement. Thus the theoretical model may be used for predicting the performance of such systems in the future.

Heat transfer analysis in environmental control using an underground air tunnel

A passive summer cooling technique that utilizes the underground soil temperature has application in climate control of residential as well as agricultural buildings. The soil temperature stays fairly constant at a depth of eight feet or more. Earlier studies have shown the usefulness of this technique for an open-loop system. However, the previous analyses in the literature did not evaluate the usefulness and limitations of this method for closed-loop air conditioning. In this study an analysis of the coefficient of performance (COP) of a closed-loop system, based on the above technique, in combination with a conventional air conditioner, has been done. In this system, the cooling needed to neutralize the heat gain of the conditioned space is provided by the air cooled in an underground air pipe in combination with an air conditioner. The underground air tunnel is used for hot parts of days and is off for cooler parts of days and nights. The analysis has been done by a computer model solution, using central finite difference method.

Performance analysis of a closed-loop climate control system using underground air tunnel

When solar arrays (photovoltaic, thermal, etc.) are arranged in multiple rows of modules, all but the first row suffer reduction in (power) output, even when sufficient spacing between rows is provided. The reduction in output power occurs because the first row prevents some of the diffuse and reflected radiation from reaching the row directly behind it. This work presents estimates of the effect of shading on the amounts of solar radiation received by consecutive rows of flat-plate arrays.

Effect of row-to-row shading on the output of flat-plate south-facing photovoltaic arrays

It can be seen from the test results that for the coil flow rate range of interest in solar DHW systems submersed coil heat exchangers can have effectiveness values as low as 0.3 for double-wall coils. This translates into a penalty of 12 to 15 percent for system performance. Inlet and outlet temperatures for the coil are easily measured. The average tank fluid temperature can be determined by inserting a thermocouple rod into the tank along the centerline. The effectiveness of submersed coils is a function of both flow rate and temperature differential between T /SUB coil/ /SUB in/ and T /SUB tank/ . For the purposes of system performance calculations, using programs such as FCHART and SOLCOST which require a single value of epsilon as input, an average value of epsilon can be chosen, representative of the coil flow rate and an intermediate value of temperature differential. This approximation introduces negligible error into the system performance results due to the relative insensitivity of the heat exchanger penalty factor, F' /SUB R/ /F /SUB R/ , with variations in epsilon for epsilon values above 0.5.

D. Y. Goswami

Papers

Heat transfer analysis in environmental control using an underground air tunnel

Performance analysis of a closed-loop climate control system using underground air tunnel

Effect of row-to-row shading on the output of flat-plate south-facing photovoltaic arrays

Thermal performance of submerged coil heat exchangers used in solar energy storage tanks