176. In case of a vertical tube evaporator, with increase in the liquor level, the __________ is increased.
177. Electromagnetic radiations propagate in vacuum with a velocity of __________ metre/second.
178. Heat flux is the time rate of heat transfer per unit
179. Film boiling occurs at __________ pressure.
180. Heat flux through several resistances in series in analogous to the current flowing through several
181. Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the
182. Vacuum is generally maintained in the vapour space of an evaporator mainly to
183. Double pipe heat exchangers are used
184. Nusselt number (for forced convection heat transfer) is a function of the __________ number.
185. Which type of heat exchanger is preferred for heavy heat loads ?
186. While the total emissivity of a perfect black body is unity, the same for a real body is
187. The Grashoff number is defined as the ratio of the
188. According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor)
189. The absorptivity of a body is equal to its emissivity
190. Absorptivity and refletivity of a perfect black body are respectively
191. In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)
192. When warm and cold liquids are mixed, the heat transfer is mainly by
193. A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ?
194. Vent pipes are provided in a condenser to
195. Heat transfer by natural convection is enhanced in system with
196. In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid.
197. A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes.
198. In forced convection, the Nusselt number is a function of
199. At what value of Prandtl number, the hydrodynamic and thermal boundary layers are identical ?
200. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because