Figure CQ10.14

You have a spherical heater, outside diameter = 3.40 cm, immersed in a container of water. In order to keep the water in the container heated to a constant temperature of 35.0°C you adjust the temperature of the spherical heater. You reach a steady-state condition when the surface temperature of the spherical heater is at 79.0°C. Assuming the electrical efficiency of the heater is 100.0%, calculate the power required by the heater (i.e., calculate q). Ignore radiation.

Estilos Edición P5. A rigid container contains water vapor at 250°C and an unknown pressure. When the container cools to 150°C, the vapor begins to condense. Estimate the initial pressure in the container. Plot the thermodynamic process on a phase diagram. Answer: 600 kPa.

A cylinder container is divided into two equal sections by thermally isolated, frictionless piston,as shown in the figure. One section contains water and the other air. The cylinder is isolated except the one face of the water section. Each section has an initial volume of 100 liter. The initial temperature of the air is 40 degees C and the water is 90 degrees C with steam quality of 10%. The water are heated slowly until the entire section of the water is filled with saturated steam. Find the final pressure and the amount of heat transported to the container. Assume: the heat transfer is a reversible process. Assume for ideal gas the following relation between p and v: (p2/p1)^((k-1)/k) = (v1/v2)^k-1 ; k=1.4

Aà

In this problem you will consider the effect that thermal expansion due to temperature will have on Archimedes' principle. Take the densities of water and copper at 0ºC to be 1.00 × 103 kg/m3 and 8.90 × 103 kg/m3, respectively. a.  Calculate the fraction of a copper block’s weight that is supported by the buoyant force at 0°C.  b. Calculate the fraction of a copper block’s weight that is supported by the buoyant force at 95°C. Assume the volume expansion coefficient of copper is βC = 5.10 × 10-5 1/°C.

D,e,f

You wish to buy a new freezer for your basement. The primary use of the freezer will be to prepare ice for family parties. You have a very large family, with grandparents, parents, sisters, brothers, uncles, aunts, cousins, nephews, nieces, and grandchildren. As a result, family birthday parties are held every couple of weeks, and you need lots of ice for drinks. You want the freezer to convert 10.5 kg of water at 23.5°C to 10.5 kg of ice at -8.6°C in 2.00 h. But, in order to keep your electric bill down, you want the power rating of the freezer to stay below 100 W. From these requirements, you determine the minimum COP of the freezer that will satisfy your needs. (Consider that the specific heat of water is 4,186 J/(kg. °C), the specific heat of ice is 2,090 J/(kg. °C), the latent heat of fusion of water is 3.33 x 105 J/kg, and the latent heat of vaporization of water is 2.26 x 106 J/kg.) COP = Need Help? Read It