126. A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2.K. The Biot number is
127. Analogy between mass and heat transfer is not applicable in case of
128. A __________ surface has the maximum thermal emissivity out of the following.
129. Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.)
130. Mechanical recompression evaporation is used in the production of
131. A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.
132. Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be
133. The purpose of providing a 'catchall' in the vapor line of an evaporator is to
134. What is the thermal conductivity of a perfect heat insulator ?
135. 'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a
136. A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to
137. Prandtl and Reynolds analogy are same, when Prandtl number is
138. Heat transfer occurs by natural convection because change in temperature causes difference in
139. The ratio of kinematic viscosity to thermal diffusivity is called the __________ number.
140. The critical radius 'r' of insulation on a pipe is given by
141. As per Kirchoffs law, the ratio of the total radiating power to the absorptivity of a body depends on the
142. If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid
143. The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by
144. __________ paint has the maximum absorption coefficient.
145. Which of the following ores does not contain iron?
146. Steam traps are provided in steam carrying pipelines to
147. The Dietus-Boelter equation for convective leat transfer
cannot be used for
148. A hot liquid is kept in a big room. The logorithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an
149. Radiation heat transfer rates does not depend upon the