Q3: A 33.8-lb aluminium bar, initially at 200 oF, is placed in a tank together with 249 lb of liquid water, initially at 70°F, and allowed to achieve thermal equilibrium. The aluminium bar and water can be modeled as incompressible with specific heats O.216 Btu/lb °R and 0.998 Btu/lb °R, respectively. For the aluminium bar and water as the system, determine (a) the final temperature, in °F, (b) the amount of entropy produced within the tank, in Btu/oR. Ignore heat transfer between the system and its surroundings.

A person is trying to keep cool on a hot summer day by using a fan and exposing his/her body to air flow. The air temperature is To = 32°C, and the fan is blowing air at a velocity of vo = 5 m/s. The surrounding surfaces are at Tsur = 40°C, and the emissivity of the person can be taken as ɛ = 0.9. If the person is doing light work and generating sensible heat at a rate of 90 W, determine the average temperature of the outer surface of the person. The average human body can be treated as a 30-cm diameter cylinder with an exposed surface area of 1.7 m?.

A 1 m diameter cylinder, 1 m long, is maintained at 800 K and has an emissivity of 0.65. Another cylinder, 2 m in diameter and 1 m long, encloses the first cylinder and is perfectly insulated. Both cylinders are placed in a large room maintained at 300 K. Calculate the heat lost by the inner cylinder.

Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in °K) A. +4 T4 B. C. D. O 1 t4 1 T4

Question 1.2 A helical coil cooler is used to cool 0.5 kg.s¹ of hot oil from 100°C down to 40°C. Cooling water with an inlet temperature of 10°C flows inside the coiled tube. The specific heat of the oil is 2 kJ.kg¹.K¹, the specific heat of the water is 4.2 kJ.kg¹.K¹, and the density of water is 1000 kg.m. a) Determine the lowest possible cooling water flow rate. (0.48 kg.s¹) b) Determine the inside diameter of the tube if a cooling water flow of 1.5 times the minimum is used, and the recommended flow velocity is 1 m.s. Select an appropriate tube from the following standard sizes: Outside diameter (mm) Wall thickness (mm) 30 1.5 35 2.0 40 2.0 45 2.5 50 3.0 c) For a heat transfer coefficient of U = 800 W.m2.K, determine the heat transfer surface area and the tube length of the heat exchanger. The oil inside the tank is mixed by a stirrer and the oil temperature at any location in the tank can be assumed to be equal to the oil outlet temperature. (Area = 4.12 m², length = 39.7 m)

A 7 dm3 rigid tank contains 4.5 kg of saturated water (liquid and vapor) at 38ºC. The tank is slowly heated. a. After a long period of time what do you think happened to the liquid water surface: do you think it raised and reached the top of the tank or it dropped and reached the bottom of it? b. Solve the same problem considering that the amount of water is 0.45 kg instead.

As shown in the figure below, a reversible power cycle receives energy QH by heat transfer from a hot reservoir at TH and rejects energy Qc by heat transfer to a cold reservoir at Tc. Hot reservoir Boundary- ZOH R Cold reservoir O at-T (a) If TH=600 K and Tc=400 K, what is the thermal efficiency? (b) If TH-500°C, Tc-20°C, and Wayde 200 kJ, what are QH and Qc. each in kJ? (c) If n = 50% and Tc= 40°F, what is TH, in °F? (d) If n = 40% and TH - 727°C, what is Tc. in °C? W cycle