Question

A closed, rigid steel tank contains 1 lbm of water, initially at 260F and a quality of 60%. The tank is fitted with a paddle wheel and the water is stirred until the temperature is 350F. The tank is well insulated on the outside and the steel is in thermal equilibrium with the water. The mass of the steel tank itself (not including water) is 60 lbm and the specific heat of the tank is 0.115 Btu/lbm·R. Changes in kinetic and potential energy are negligible.

1)Determine the pressure of the water at the final state, in lbf/in^2

2) Determine the work done, in Btu

3) Determine the amount of entropy produced for a system including both the water and the steel tank, in Btu/degrees R.

Answer #1

A closed, rigid steel tank contains 1 lbm of water, initially at
260 F and a quality of 60%. The tank is fitted with a paddle wheel
and the water is stirred until the temperature is 350 F. The tank
is well insulated on the outside and the steel is in thermal
equilibrium with the water. The mass of the steel tank itself (not
including water) is 60 lbm and the specific heat of the tank is
0.115 Btu/lbm·R. Changes...

A closed, rigid tank is filled with water. Initially, the tank
holds 1.0 lb of saturated vapor and 7.0 lb of saturated liquid,
each at 212°F. The water is heated until the tank contains only
saturated vapor. Kinetic and potential energy effects can be
ignored. Determine the volume of the tank, in ft3, the temperature
at the final state, in °F, and the heat transfer, in Btu.

A 50 kg copper block initially at 350 oC is quenched in a
closed, rigid insulated tank containing 120 L of liquid water at 25
oC. Specific heat of copper, Cc = 385 J/(kgK), specific heat of
liquid water, Cw = 4180J/(kgK). (i) Calculate the entropy change
(kJ/K) of copper block. (ii) Determine the entropy change (kJ/K) of
liquid water.

Initially (state 1) a well-insulated rigid tank contains 20 kg
of a saturated liquid-vapor mixture of water at 100 kPa and half of
the mass is in the liquid phase. An electric resistance heater
placed in the tank is now turned on and kept on until all the
liquid in the tank is vaporized (state 2). Determine (a) the
initial specific volume in m3/kg, (b) the final specific
entropy in kJ/kg.K and (c) change of entropy in kJ/K.

Initially (state 1) a well-insulated rigid tank contains 20 kg
of a saturated liquid-vapor mixture of water at 100 kPa and half of
the mass is in the liquid phase. An electric resistance heater
placed in the tank is now turned on and kept on until all the
liquid in the tank is vaporized (state 2). Determine (a) the
initial specific volume in m3/kg, (b) the final specific
entropy in kJ/kg.K and (c) change of entropy in kJ/K.

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