8/9/2019 CFD Study of Air Flow and Heat Transfer in Solar Collector With and Without Porous Media

1/4

Name : Mark Tang Tak Yan

ID : 1041111141

CFD study of air flow and heat transfer in solar collector with and

without porous media

Introduction

Today, the heat transfer characteristic and performance of the solar collector with and without

porous media are continuously studied numerically. Mathematical models are being developed which

are derived by using the energy equations. In this study,the thermal conductivity of the porous media is

considered.

The main objective of a solar collector is to achieve maximum amount of energy collected with

minimal cost. It is extensively used in residential, industrial and agricultural field. The heat transfer

characteristics of the solar collector have been widely studied. Yen and Linitheoretically and

experimentally studied the effects of collector aspect ratio of the collect on flat-plate, upward and

baffled solar collectors. Ongii

predicted the thermal performance of four common types of single-pass

solar air heaters. Fathiii

studied the thermal performance of a simple design solar air heater. Al-Kamil

and Al-Ghareebiv

experimentally and theoretically studied the effects of the various parameters, such as

temperature, solar intensity and air flow rate on the performance of a flat plate solar air heater.Sopian

et al.vexperimentally studied on the thermal performance of the double-pass solar collector with and

without porous media in the second channel.Naphon and Kongtragoolvi

applied the mathematical

models for predicting the heat transfer characteristics and performance of the various configuration offlat-plate solar air heater.

As described above, there are many studies on the solar air heater. However, the studies on

heat transfer characteristics of the double-pass flat plate solar collector with porous media are still

limited. The objective of this paper is to study theoretically on the heat transfer characteristic and

performance of the double- pass flat plate solar collector with and without porous media using

computational fluid dynamics (CFD). The effects of various relevant parameters on the model prediction

are also investigated.

8/9/2019 CFD Study of Air Flow and Heat Transfer in Solar Collector With and Without Porous Media

2/4

Literature Review

The basic physical equation used to describe the heat transfer characteristics are developed

from the conservation equations of energy. The model is based on that of Naphon and Kongtragool6

with the following assumptions.

y The air flow at the inlet is steadyy The inner and outer convective heat transfer coefficient is constant along the length of the solar

collector

y The thermal conductivity of the porous media is constant along the length of the solar collector.

Fig.1. Schematic diagram of the solar collector without (A) and with (B) porous media

Absorber

Glass

Air Inlet

Air Outlet

Air Inlet

Air Outlet

Absorber

Insulation

Insulation

Porous

Media

8/9/2019 CFD Study of Air Flow and Heat Transfer in Solar Collector With and Without Porous Media

3/4

For top glass cover

(1)

WhereI is the solar intensity, c is the absorptivity of the glass cover, ha is the heat transfer coefficient

between the ambient and the glass, Tc is the glass cover temperature, Tp is the absorberplatetemperature, Ta is the ambient temperature, Tf1 is the fluid temperature in the top channel, and

hr,cp andhr,ac are the radiative heat transfer coefficients between the glass cover and the absorber plate,

the glasscover and ambient, respectively, as follows (Fig. 1):

(2)

(3)

For first-pass air stream

(4)

wherem is the mass flow rate of fluid per unit width, Cp is the specific heat of working fluid, hfc1 is the

heat transfer coefficient between the glass cover and working fluid, and h f1p is the heat transfer

coefficient between the absorber plate and working fluid.

For absorber plate

(5)

where is the absorptivity of the absorber plate, is the transmitivity of the glass cover, and is thefluid temperature in the bottom channel.

For second-pass air stream without porous media

(6)

For second-pass air stream with porous media

8/9/2019 CFD Study of Air Flow and Heat Transfer in Solar Collector With and Without Porous Media

4/4

(7)

For bottom plate

(8)

where is the overall heat transfer coefficient, is the bottom plate temperature, and is thethermal conductivity of the porous media.

Computational Fluid Dynamics (CFD)

Computational fluid dynamics, CFD, is a computational technology that enables the study ofdynamics of things that flow. Using CFD, a computational model can be built according to the desired

requirement. Flow physics can be applied to the model and an output prediction of the fluid dynamics

and related physical phenomena can be obtained. It is also a sophisticated computational-based design

and analysis technique.

CFD has the power to simulate flows of gases and fluids, heat and mass transfer, fluid structure

interaction and acoustic through computer modeling. By using CFD, we can create a virtual prototype

which we want to analyze and apply the required physical characteristic or any real world physics which

in turn will predict the outcome and performance of the desired model.

In this study, we will be using the software from ANSYS for CFD. With this software, we will

have to build a virtual model of the double pass solar collector with and without porous media. From

there, we are able to determine the output prediction of the air flow and heat transfer in this solar

collector. By using the virtual model, we are able to manipulate the values and characteristic of the solar

collector to achieve the optimum heat transfer and air flow. All this values obtained from the CFD

software are theoretical, so we would need to compare the experimental results which are done by K.

Sopianv.

References

iH.M. Yeh, T.T. Lin, Energy (1995)

iiK.S. Ong, Solar Energy (1995)

iiiH.E.S. Fath, Energy Conservation and Management (1995)

ivM.T. Al-Kamil, A.A. Al-Ghareeb, Energy Conservation and Management (1995)

vK. Sopian, Supranto, W.R.W. Daud, M.Y. Othman, B. Yatim, Renewable Energy (1999)

viP. Naphon, B. Kongtragool, International Communications in Heat and Mass Transfer (2003)

viiBAA Yousef, NM Adam, Journal Of Energy in Southern Africa (2008)