Performance Analysis of Solar Chimney

Submitted to - Presented by-

Mechanical Engg. Dept. Robin Jain

MNIT 2014PTE5059

M.Tech Thermal Engineering

MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY, JAIPUR

Introduction

Solar chimney (SC) is a passive element that make use of the solar energy to induce buoyancy-driven airflow and naturally ventilate the building.

Solar Chimney is a passive device that Enables heating of air in the tower. As air heated in the tower, it rises up and create

upward draught

Source: Rakesh

et. al. (2011)

Working Principle of Solar Chimney

The system uses the solar energy. The temperature difference between the outdoor temperature

air in the chimney and the air temperature in the attached room promotes movement of air

The rate at which air is drawn through the room depends upon the buoyancy-force experienced, (i.e. dependent upon the temperature differential), the resistance to flow through the chimney, and the resistance to the entry of fresh air into the room.

Source: D. J. Harris

et. al. (2007)

Solar Chimney

Types of Solar Chimney

There are four general types of solar chimney:

1. Open loop system

2. Closed loop system

Types of Solar Chimney

Type 1 Type 2

Types of Solar Chimney

Type 3 Type 4

Advantages and Disadvantages of Solar Chimney

Advantages: 1. simple to use and easy to maintain.

2. low maintenance cost and the electricity cost saving

3. no harmful impact on the environment.

Disadvantages: 4. High initial investment cost.

5. Recommended for new houses which has excellent insulation and air-tightness.

6. Space requirement is the major hindrance.

7. Skilled man power required for well designing of system.

Applications of Solar Chimney

Solar Chimney can be used in a vast variety of fields:

In the generation of electricity Integrated in buildings as a natural ventilation device Sunrooms can also be designed to function like solar

chimneys Integrated in buildings as a heating device

Mathematical Modeling of Solar Chimney

Physical Model

Thermal Network

Mean air temperature can be find out using above equations

Modelling of Solar Chimney (cont.)Air flow rate can be find out using given equation

Heat transfer from glass cover to ambient can be find out using given equation

Modelling of Solar Chimney (cont.)Heat transfer between wall and glass cover can be find out using given equation

Conduction heat transfer from vertical wall to room can be find out using given equation

Solar radiation heat flux normal to and absorbed by the glass cover is given by

Solar radiation heat flux absorbed by the blackened wall is given by

Modelling of Solar Chimney (cont.)The instantaneous efficiency of heat collection by the solar chimney is given by

Physical properties of air is given by

Experimental SetupRectangular box2.00 m highX0.48 m wideX1.02 m deep.

Top, base and side wall were fabricated from22 mm thick rigid polyurethane sheets laminated both sides with 1 mm thick steel sheet.

4 mm thick glass glazing

50 mm thick rigid polyurethane sheetFor heat absorbing wall

Width of air gap is 0.45m

Orientation of solar chimney towards south

Results of Experimental Analysis

Location of Thermocouple Points

Air Temperature Distribution

Temperature distribution across air gap depth (d = 0.1 m)

Mean Wall, Air and Glass Temperature

Typical air, glass and wall temperature distributions along the chimney

10:24 am16 January 2002H = 670 W d = 0.1 m

Effect of Incident Solar Radiation

Variation of mean glass, wall and air temperatures, air volumetric and mass flow rates, and instantaneous efficiency with solar radiation (d = 0.1 m)

Effect of Incident Solar Radiation (cont.)

Variation of mean glass, wall and air temperatures, air volumetric and mass flow rates, and instantaneous efficiency with solar radiation (d = 0.2 m)

Effect of Incident Solar Radiation (cont.)

Variation of mean glass, wall and air temperatures, air volumetric and mass flow rates, and instantaneous efficiency with solar radiation (d = 0.3 m)

Effect on Inlet Air Flow Velocity

Mea Inlet air flow velocity variation with air gap depth and incident solar radiation

Effect on Instantaneous Efficiency

Instantaneous efficiency variation with air gap depth and incident solar radiation

Comparison between theoretical Predictions and experimental

results

Experimental v/s Theoretical Results

Experimental and predicted mean glass, wall and air temperatures (H = 650 W )

Experimental v/s Theoretical Results

Experimental and predicted mean glass, wall and air temperatures (H = 200 W )

Experimental v/s Theoretical Results

Experimental and predicted mean air temperature rise, inlet air flow velocity, And instantaneous efficiency (H = 650 W )

Experimental v/s Theoretical Results

Experimental and predicted mean air temperature rise, inlet air flow velocity, And instantaneous efficiency (H = 200 W )

Parametric Analysis of Solar Chimney

Case Study

Building Description

Conclusion

No reverse flow was observed up to 0.3 m gap The experimental and theoretical results have more satisfactory

agreement for large air gap.

References

[1] K.S. Ong*, C. C. Chow, Performance of a Solar Chimney.

Thank you