Q1: The absorption of ammonia from a mixture of ammonia and air containing 10% of ammonia by volume, using pure water as solvent. Assume that all the resistance to mass transfer lies within the gas phase. By what percentage would the rate of absorption be increased or decreased by increasing the total pressure from 100 to 200 kN/m². The diffusivity can be assumed to be inversely proportional to the absolute pressure.

Problem 3 Helium gas at 25 °C and 4 bars is contained in a spherical glass container of 200 mm inside diameter and 10 mm thickness. If a constant stream of air is passed over the exterior of the vessel, what is the initial rate of mass loss from the container? Assume, the diffusivity of helium through the glass is 0.4 x 10-¹3 m²/s and the molar solubility of helium in the glass is 0.45 x 10³ kmol of He/(m³of solid bar of He).

3 An electrical current of 700 A flows through a stainless steel cable having a diameter of 5 mm and an electrical resistance of 6 x 104 /m (i.e., per meter of cable length). The cable is in an environment having a tem- perature of 30°C, and the total coefficient associated with convection and radiation between the cable and the environment is approximately 25 W/m².K. (a) If the cable is bare, what is its surface temperature? (b) If a very thin coating of electrical insulation is applied to the cable, with a contact resistance of 0.02 m² K/W, what are the insulation and cable surface temperatures? (c) There is some concern about the ability of the insula- tion to withstand elevated temperatures. What thick- ness of this insulation (k = 0.5 W/m .K) will yield the lowest value of the maximum insulation temper- ature? What is the value of the maximum tempera- ture when this thickness is used? Note: The 25 W/m²K includes not only convection but also radiation.

Quiz2: Determine the value of specific entropy of steam at 2Mpa with temperature 400 °C. A) by calculation B)by steam table