15.07.2015   EuroSun2008-4

Theoretical study on a diurnal solar chimney with double air flow

J. Arce1,2,3, J. Xaman2, G. Alvarez2, M. J. Jimenez3, J. D. Guzman3 and M. R. Heras3

1 CIE-UNAM, Centro de Investigacion en Energia, Priv. Xochicalco S/N Col. Centro, Temixco, Morelos, CP 62580, Mexico

2 CENIDET-DGEST-SEP, Department of Mechanical Engineering, Centro Nacional de Investigacion y Desarrollo Tecnologico, Prol. Av. Palmira S/N. Col. Palmira.

Cuernavaca, Morelos, CP. 62490, Mexico

3 CIEMAT, Department of Energy, Energy Efficiency in Buildings Unit, CIEMAT,

Madrid, E-28040, Spain.

Corresponding Author, j earl@cie. unam. mx

Abstract

A theoretical study on a solar chimney for diurnal use with double air flow is performed.

The chimney’s dimensions are; 2.0 m height, 1.0 m width, and 0.15 m depth for both flow channels. The principal element is a metallic plate between double glass cover, one side toward the East and the other one toward the West. Glazing is used in order to decrease the radiation and convection losses to the environment. Two air inputs at the bottom and two air outlets at the top are used. For some established environmental conditions, the energy conservation equations are resolved for each element of the chimney in order to calculate the temperature distribution, the efficiency of the system and the mass flow rate. The model was verified with the results reported in the literature for a reduced problem of a single flow chimney, obtaining very good agreement. For an irradiance of 500 W/m2, a maximum mass flow rate of 0.06 kg/s was calculated for the double air flow chimney.

Keywords: Solar chimney, natural convection, ventilation

1. Introduction

Nowadays, natural ventilation in the design of buildings is one of the important requirements, mainly because contamination or energy savings. Ventilation is the movement of air from the exterior to the interior. It is very important to replace the inner air in any building in order to enhance the air quality and the thermal performance. In the last three decades, the study of ventilation has been increasing among the scientific community. Earlier, there existed very few studies of natural ventilation systems in the literature. This fact may be due to the use of conventional systems, such as air conditioning systems and air heating systems to create artificial environments. However, it is well known that oil is rapidly decreased; besides air pollution is another issue that needs to pay attention. Passive systems such solar chimney may contribute to decrease the use of conventional fuels and also improve the environment of buildings. A solar chimney is defined as a kind of long ventilated heated cavity that should be installed in buildings in sunny places. Small and real scales models have been studied [1, 2-6]. However, the performance of solar chimneys is not completely understood.

2. Objective

The objective of this paper is to study numerically the thermal performance of a full scale two air flow solar chimney and modify parameters that predict the thermal performance of the system under particular environmental conditions.

 
image244

Glazing 1 ■

Blackened metallic absorbing plate ж

 

Glazing 2

Solar

radiation

 

Solar

chimney

 

Bottom

opening

 

Bottom

opening

 

Room

image245

 

(a) (b)

Fig. 1. (a) Schematic diagram of a solar chimney. (b) Physical model.

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