Molecular Physics | Thermodynamics Answers

Calculate the decrease in available energy when 25 kg of water at 95oC mix with 35 kg of water at 35oC, the pressure being taken as constant and the temperature of the surroundings being 15oC. (Cp of water = 4.2 kJ/kg K).b.Find entropy, enthalpy and specific volume of steam at 173oC.

mercury manometer is connected to open tank of fuel (Fig 8). Calculate a change of manometer readings

h if a level of fuel increases by ΔH. Take ΔH=0.2m, ρf=832 kg/m3, ρm=13600 kg/m3.

Suppose an empty balloon weighs 50 g and that it has a diameter of 1.5 m when it is helium filled. The density of air is 1.3 kg/m3, and the density of helium is 0.18 kg/m3. Calculate the maximum lifting force that the balloons can exert. 

In an attempt to determine the specific heating capacity of copper, the following experiments were used. A copper cylinder weighing 145 g is placed in a large tub of water with a temperature of 94.0  oC. When the cylinder has been in this warm water for along time, it is lifted up and put in a thermos with 335 g of water with a temperature of 12.0  oC. This water is then heated up to 15.4  oC. What value of copper's specific heat capacity does this experiment provide? The specific heat capacity for water is 4.18·103  

A two stage single acting air compressor with complete intercooling takes in air at 1 bar and 288k at rate of 360kg/h.The delivery pressure is 16 bar. Calculate the power required,the isothermal efficiency ,FAD and the net heat transferred in each cylinder and the intercooler . Take the index of compression and expansion for both stages is 1.3. The speed of the compressor is 420rpm. If the clearance ratios for the LP and HP cylinders are 0.06 and 0.08 respectively , calculate the swept and clearance volumes for each cylinder.

A three-stage, single acting compressor is required to compress 135m3 of free air per hour from 1bar to 64bar. Prove that with complete intercooling the stage pressure ratio should be equal to the cube root of the overall pressure ratio for the required power to a minimum. Calculate the power needed in each case, assuming n = 1.3.

If the mean piston speed is to be 140 m/min, calculate the piston areas, neglecting clearance. State any assumptions made.

A gas – turbine plant operates on the ideal cycle. The air enters the compressor at 1 bar, 15°C, and is delivered at 6 bar; the temperature at turbine inlet is 650°C. Determine per kg of air.

a) the compressor work

b) the turbine work

c) the heat supplied

d) the heat rejected

e) the thermal efficiency of the plant

Assume the working fluid to have the properties of air throughout, and take cp = 1.005 kJ/kg K and γ = 1.4.