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Consider the following statements (i) If a condensing liquid does not wet a surface, then drop wise condensation will not take place on it (ii) Drop wise condensation gives a higher transfer rate than film wise condensation (iii) Reynolds number of condensing liquid is based on its mass flow rate (iv) Suitable coating or vapor additive is used to promote film wise condensation Identify the correct statement

Correct Answer: i, ii and iii
All are correct except the last one because suitable coating or vapor additive is not used to promote film wise condensation.

Statement 1: Film-type condensation has a higher heat transfer co-efficient than drop-wise condensation. Statement 2: Drop-wise condensation is easier to maintain than Film-type condensation

Consider the following statements regarding nucleate boiling (i) The temperature of the surface is greater than the saturation temperature of the liquid (ii) Bubbles are created by the expansion of entrapped gas oil vapor at small cavities in the surface (iii) The temperature is greater than that in film boiling (iv) The heat transfer from the surface to the liquid is greater than that in the film boiling Which of these statements are correct?

Statement 1: Drop-wise condensation takes place on a smooth surface. Statement 2: All the resistance to heat transfer lies in the film formed during Film-type condensation.

In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m2 hr degree. Find the number of transfer units of the heat exchanger. At the condensing pressure, stream has saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to water. Take specific heat of water as 4 k J/kg K

A stream of air at 100 kPa pressure and 300 K is flowing on the top surface of a thin flat sheet of solid naphthalene of length 0.2 m with a velocity of 20 m/sec. The other data are: Mass diffusivity of naphthalene vapor in air = 6 * 10 –6 m2/sec Kinematic viscosity of air = 1.5 * 10 –5 m2.sc Concentration of naphthalene at the air-solid naphthalene interface = 1 * 10 – 5 kmol/m3 Calculate the overage mass transfer coefficient over the flat plate. Note: For heat transfer over a flat plate, convective heat transfer coefficient for laminar flow can be calculated by the equation. Nu = 0.664 ReL1/2 Pr1/3 you may use analogy between mass and heat transfer.

If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.

Consider the following statements pertaining to heat transfer through fins (i) They must be arranged at right angles to the direction of flow of working fluid (ii) The temperature along the fin is variable and accordingly heat transfer rate varies along the fin elements (iii) Fins are equally effective irrespective whether they are on the hot side or cold side of the fluid (iv) Fins are made of materials that have thermal conductivity higher than that of wall Identify the correct statements

Consider the following statements about emulsion SBR and solution SBR. I. Solution SBR has higher content of non-rubber materials than emulsion SBR II. Solution SBR has higher molecular weight but broader molecular weight distribution than emulsion SBR III. Solution SBR has higher cis-1,4-polybutadiene content than emulsion SBR Which of the following statements are true?

In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m2 hr degree. Find the effectiveness of the heat exchanger. At the condensing pressure, stream has a saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to the water. Take specific heat of water as 4 k J/kg K

Examine the following statements :
i) Factor of safety for steel should be based on its yield stress,
ii) Factor of safety for steel should be based on its ultimate stress,
iii) Factor of safety for concrete should be based on its yield stress,
iv) Factor of safety for concrete should be based on its ultimate stress.
The correct statements are