Answer:
A selective surface with large absorption for solar radiation and high reflectance for thermal infrared radiation was produced by use of surface oxidation of stainless steel. The surfaces were studied for use with concentrated light in a solar power plant at temperatures of 400°C and higher.
In order to investigate the relation between surface treatment and optical properties, stainless steels (AISI 304 and 430) which were submitted to different chemical and mechanical surface treatments, were used. To increase the spectral selectivity, these surfaces were treated in air and in vacuum at different temperatures and times. The optical properties of these films were investigated. Visual and infrared spectral absorptances were measured at room temperature. The thermal hemispherical emittance and absorptance were obtained by a calorimetric method at 200°C. It was noticed that these chemically and mechanically treated stainless steel surfaces have good spectral properties without further oxidations. This is very important for high temperature uses. The best values are found for samples 7 and 8 under vacuum and air. These two samples with mechanically ground surfaces retained their selectivity and specularity after several hours oxidation. One can conclude that the surface ground treatment confers good selectivity on the steel surfaces for use in concentrating solar collectors with a working temperature of 500°C.
Sample surfaces were subjected to long temperature ageing tests in order to gain some idea of the thermal stability of the surfaces. The results promise better-performing surface and the production of durable selective finishes at, possibly, lower cost than competing processes.
Explanation:
Answer:
D
Explanation:
Most electric vehicles can go at least 100.....few, if any, can go 400 or more on a single charge
Find the solution in the attachments
Note: Question was incomplete, so the complete question is added in the attachments.
Answer:
a. Heat removal rate will increase
b. Heat removal rate will decrease
Explanation:
Given that
One end of rod is connected to the furnace and rod is long.So this rod can be treated as infinite long fin.
We know that heat transfer in fin given as follows
We know that area
Now when diameter will triples then :
So the new heat transfer will increase by 3 times.
Now when copper rod will replace by aluminium rod :
As we know that thermal conductivity(K) of Aluminium is low as compare to Copper .It means that heat transfer will decreases.
Answer and Explanation:
Pyroelectric material
Pyroelectric materials have special property of generating potential difference (although it is very less ) when these material are treated with heat or when celled down.
The potential difference generated is for very less time
The generation of potential difference is due to change in position of atoms after heating or cooling.
