Question

The central receiver of a solar power plant is in the form of a cylinder 7m in diameter and 13 m high. A tower supports the receiver high above the ground, and solar radiation is reflected to the receiver by rows of reflectors at ground level. The operating temperature of its surface is 700K and the temperature of the still ambient air is 300 K. The total irradiation of the collector is 20 MW.

Perform a parametric analysis to study the effect on the heat convection coefficient and the percentage of loss of heat transfer rate due to the variation of the following variables: height, surface temperature, ambient temperature and wind velocity.

Answer 1

Given solution:-

      Verticle cylinder present at 400k. We have to find conventive heat loss into fill ambient air.

Assume.. 1) Curvature effect are very much so not consider.

               2) The free- Convection boundary layer commences at the bottom of the cyclinder .

We have to first all find the Ray leigh number (RAL) Which is given by.

RAL=GrL(Grashof number) xPr( Prandtl number)

                              (1)

From the gasas thermal properties table we can find the for air at a means film temperature.

                 

                   

                     

                  

Putting these valus in (1), we got

        

        

The above Ray leigh number is approx close to the turbulrnt float upper limit. so, we have to use the average nusselt number for turbulent flow.

                      (2)

Here, = Parndtl number function

Putting RaL.... & value in (2), we get

    

     

                      

                      

                      

                      

           

    Hence, convetive heat loss into still ambient air at 300k is 0.18373 MW.