h of the following is not an assumption that Nusselt made in analytically deriving the average heat transfer coefficient over a vertical surface surrounded by vapor undergoing film condensation? A. Film thickness is zero at the top of surface B. Falling film is undergoing laminar flow C. Heat transfer from the condensing vapor to the surface is happening via natural convection D. All the assumptions above are important to the film condensation problem

Use the Kedzierski (2003) refrigerant/lubricant mixture pool boiling model to predict the boiling heat transfer coefficient (hm) for a range of superheats (4T, = 8 K to 40 K) and Ts = 277.6 K: 5.9×107(1−x,)ph ATk, (1-e*) x, To Where 1₂ %₁ = = 9m T-T Г x Τσ PL-Pbx 5.9×107(1-x₂)ph AT 0.755lp₁ (1-x₁) _ 18.75õ₁ (1—x₁) _ 18.75×10¯¹º[m]p, (1-x₂) Xp Prv XpPrv XpPrv Assume that λ = 1.34 for xb=0.005 and that λ = 0.3 for Xb = 0.02. The properties of the refrigerant (R123) at the film temperature are: KL (W/mK) 0.139 R123 Or (N/m) 179692.3 0.01764 hfg (J/kg) The properties of the mineral oil (lubricant) are: PL (kg/m³) 917.8 York-C VL (cSt) 60 Prv (kg/m³) 2.701 VL (m²/s) 6 × 10-5 OL (N/m) 0.026 1.) Plot hm vs ATs and le vs ATs for two lubricant mass fractions: x = 0.005 (use 2 = 1.34 for Xb = = 0.005) and x = 0.02 (use λ = 0.3 for xb = 0.02). Compare the predicted ro for the two mass fraction cases. Provide a plausible reason for why the boiling heat transfer coefficient for a given AT's for…

*** 32. A double-chambered container contains one mole of helium in one of its 1000 cm³ Pull to volume chambers. The container is well-insulated, and of low specific heat, so that no appre- remove ciable heat is added to the gas during the process we describe. The gas is initially at a tempera- ture of 300 K and a pressure of 1 atmosphere. The partition between the two chambers is then quickly raised, and the gas expands freely to fill the entire container. Whenever a monatomic gas like helium doubles its volume adiabatically like this, the pressure in the gas will drop to 0.315 of what it was before (for reasons that we did not explain in this chapter), so the final 1000 cm3 1000 cm³ pressure of the expanded gas will be 0.315 atmospheres. a) What is the temperature of the gas after the expansion? b) What is the change in the internal energy of the gas? c) How much heat is added to the gas? [Hint: Maybe read the problem again.] d) How much work is done by the gas as it expands? [Hint:…

A 2 m wide, 3 m high, and 50 mm thick sheet of XPS insulation (M = 50 ng/Pa.s.m2), has a vapor pressure of 1500 Pa on one side, and 3500 Pa on the other. Calculate the vapor flow rate (Qv), vapor flux (qv), permeability, Rv value and the permeability (μ)