What is the correct answer?


Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be

A. One

B. Two

C. Three

D. Four

Correct Answer :

C. Three

Related Questions

Unit of thermal conductivity in S.I. units is The ratio of the emissive power and absorptive power of all bodies is… The ratio of the energy absorbed by the body to total energy falling on… 40% of incident radiant energy on the surface of a thermally transparent… The use of heat exchangers is made in Which of the following has maximum value of thermal conductivity? Radiation is the process of heat transfer in which heat flows from a ________,… The unit of overall coefficient of heat transfer is The rate of energy transferred by convection to that by conduction is… Depending on the radiating properties, body will be transparent when The critical temperature is the temperature In free convection heat transfer, Nusselt number is function of According of Kirchhoff's law Thermal conductivity of air at room temperature in kcal/m hr °C is… According to Dalton's law of partial pressures, (where pb = Barometric… In regenerator type heat exchanger, heat transfer takes place by The total radiation from a black body per second per unit area is ________… According to Newton's law of cooling, the heat transfer from a hot body… According to Wien's law, the wavelength corresponding to maximum energy… The emissivity for a black body is Total emissivity of polished silver compared to black body is In heat transfer, conductance equals conductivity (kcal/hr/sq.m/ °C/cm)… A grey body is one whose absorptivity Thermal diffusivity is The amount of radiation mainly depends on In heat exchangers, degree of approach is defined as the difference between… The highest thermal diffusivity is of Fourier's law of heat conduction gives the heat flow for In a shell and tube heat exchanger, baffles are provided on the shell… The value of the wave length for maximum emissive power is given by