Chapter 3, Problem 3.35P

A 12-by-12 in. open pan containing water at 140 °F is placed in the exact center of a 16-by-20 ft room having a ceiling temperature of 75°F. If the distance from the water surface to the ceiling is 10 ft and the ceiling is painted with an oil paint, what is the net radiant-heat exchange between the water surface and the ceiling?

A refrigeration plant stored 10 metric tons of eggs at a temperature of 15°C. To preserve the eggs by not spoiling them, they have to be cooled at -8°C. What is the refrigerating capacity of the plant in TOR if it is cooled for 12 hours? The specific heat of the eggs above and below freezing are 0.95 kcal/kg-°C and 0.4 kcal/kg-°C, respectively. The latent heat of fusion is 68.5 kcal/kg The freezing temperature is -3°C.

An engineer receives a schematic fora reversible heat engine with three reservoirs at the temperatures shown to the right. The heat engine produces 1800 kW work as it pulls 3200 kW of heat from the 600K reservoir. The engineer wonders if the schematic is drawn correctly (in other words, are the arrows going the correct directions?) To answer this question, (a) calculate the heat interactions of the HE with the other two reservoirs. (b)If necessary, draw an updated diagram with the correct directionalities indicating the rates of heat transfer.

The tip of a soldering iron consists of a 0.6-cm- diameter copper rod, 7.6 cm long. If the tip must be 204C, what are the required minimum temperature of the base and the heat flow, in watts, into the base? Assume that h=22.7W/m2KandTair=21C.

Calculate the amount of heat to be supplied to generate 10 kg/sec of steam at 12 MPa and 400°C from water at 115°C.

Calculate the amount of natural gas that you need to burn to heat 75 L of water from room temperature at 21° C to 48° C to take shower if the water heater has an efficiency of (a) 78 percent, (b) 85 percent, and (c) 90 percent.

If heated at the same rate and in the same manner, which would have a more even heat distribution during heating, a copper pan or a cast iron one? Why?

10 kg of frozen chicken at an initial temperature of -20°C is to be thawed and raised to a temperature of 10°C before cooking. The freezing point of the meat is -1.7°C and the specific heats above and below the freezing point are 3.1 kJ/kg-K and 1.6 kJ/kg-K, respectively. The heat of fusion (the amount of heat needed per unit mass to thaw chicken at the freezing point) is 233 kJ/kg. Find the total amount of heat that must be transferred to complete this the process.

A refrigerator is connected to a generator powered by a fuel with a calorific value of 35000 kJ/kg and a density of 0.85 g/cm3 . The inside temperature of the refrigerator is 0°C, and the outside temperature is 20°C. a. How much work is required to freeze 500 g of water? ΔfreezingH° = 6.02 kJ mol– 1 )   b. How much internal energy change occurs during the process?   c. Since the generator consumes 5 L of fuel per hour, calculate the thermal efficiency of this engine.