Engineering Answers

Steam at 7 bar and dryness fraction 0.9 expands in a cylinder to a pressure of 1.5 bar and 300oC. Calculate the change of internal energy and the change of enthalpy per kg of steam. 

Determine the frequency of sound heard by a stationary listener when a moving siren emits 550Hz and travels away at 50m/s from the listener assuming the air temperature is 20 degree Celsius.

 A riveted joint is shown in the figure which is used in the bridge to lock the wire, By using the information from the Figure you have to calculate the maximum bearing stress available between the pin and the members of the joint; You also need to calculate (b) the average shear stress in the pin for given load; as well as (c) the maximum mean normal stress in the joint members.

Determine the height at which the oak block will float above the water surface. The density of the oak is ρoak = 770 kg/m3

A refrigerator unit working on Bell Coleman cycle takes air from cold chamber at -10 °C and compresses it from 1 bar to 6.5 bar with index of compression being 1.2. The compressed air is cooled to a temperature of 25 °C before it is expanded in the expander where the index of expansion is 1.35, determine,

a. COP

b. Quantity of air circulated per minute for production of 2000 kg of ice per day at 0 °C from water at 20 °C

c. Capacity of the plant in tons of refrigeration Assume, C₂ = 1 kJ/kg k for air.

A Carnot refrigerator requires 1.1 kw per tome of refrigeration to maintain a region at

m'/kg respectively.

a low temperature of -30°C. Determine

a. COP of refrigerator

b. Higher temperature of the cycle

c. Heat rejected in KJ/ton

d. Calculate the heat delivered and COP, when this device is used as heat pump.

A refrigerator unit working on Bell Coleman cycle takes air from cold chamber at -10 °C and compresses it from 1 bar to 6.5 bar with index of compression being 1.2. The compressed air is cooled to a temperature of 25 °C before it is expanded in the expander where the index of expansion is 1.35, determine,

a. COP

b. Quantity of air circulated per minute for production of 2000 kg of ice per day at 0 °C from water at 20 °C

c. Capacity of the plant in tons of refrigeration Assume, C₂ = 1 kJ/kg k for air.

An air refrigerator works between pressure limits of 1 bar and 4 bar. The temperature of the air entering the compressor is 15 °C and entering the expansion cylinder is 30 °C. The expansion follows the law PV^1.25= constant. The compression follows the law PV^1.35 = constant. Take for air, Cp = 1 kJ/kg k and Cv = 0.7 kJ/kg k. Find the following

a. COP of the refrigeration cycle

b. If the air circulation through the system is 25 kg/min, find the refrigeration capacity of the system

8.) The energy required to punch a square from 30mm thick plate is 20KJ. If the ultimate strength of plate is 450Mpa, determine the maximum sides of square that can be punch. (Please show the solution of answer)

Answer: S=24.69mm

6.)  The power required to shear a plate 60mm thick for 20sec is 8KW. If the ultimate strength of plate materials is 4oo Mpa, How wide should the plate be? (Please show the solution of answer)

Answer: b= 222.22mm