Mechanical Engineering Answers

Air refrigeration works between 1 bar and 5 bar pressure limits. The temperature of the air entering the compressor and expansion cylinder is 8+A0C and 20+B0C respectively. The expansion and compression follow the law pv1.3=Constant. Find the following: • The theoretical C.O.P of the refrigerating cycle. • If the load on the refrigerating machine is 10 tons, then find the amount of air circulated per minute through the system. Assuming the actual C.O.P is 50% of the theoretical C.O.P. • Length and diameter of the single-acting compressor run at 300 r.p.m and the volumetric efficiency are 85%.

The thin-walled single cell beam shown in Figure has been idealized into a combination of

direct stress carrying booms and shear stress only carrying walls. If the section supports a vertical

shear load of 10 kN acting in a vertical plane through booms 3 and 6, calculate the distribution of

direct stress around the section.

Steam at a temperature of 623 K is flowing through a pipe with an outer diameter of 100 mm. The pipe is insulated with 20-mm thick mineral wool, the average thermal conductivity of which is 0.055 W/m.K. Determine the outside surface temperature of mineral wool if the ambient air temperature is 300 K. Assume the hot-surface temperature of the mineral wool is the same as that of the flowing steam and the value of the surface coefficient of the insulating material is 30 W/m².K.

combustion of methane with air . the volumetric analysis of the products oon a dry basis revela sthe following

A system composed of 2 kg of the above fluid expands in a frictionless piston and cylinder machine from an initial state of 1 MPa, 100°C to a final temperature of 30 degrees * C . If there is no heat transfer, find the net work for the process.

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. 

 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.