Mechanical Engineering Answers

A 0.8 m high, 1.5 m wide double pane window consists of two 4 mm

thick layers of glass (k=78 W/mK) and is separated by a 10 mm wide

stagnant air space (k=0.026W/mK). The room is at 20°C and the

outside air is at -10°C. The heat transfer coefficients are 10 and 40

W/m2K. find

i) The rate if heat transfer through the window

ii) The inside surface temperature

A piston cylinder containing steam at 700 kPa at 250 degrees celcius undergoes a constant pressure process until the quality is 70%. Determine: a). Work done b). Heat transferred c). Change in internal energy d). Change in enthalpy NOTE: - INDICATE THE PV and TS DIAGRAM - INDICATE THE INITIAL AND FINAL STATE OF THE SUBSTANCE

Ans. (a) -101.4 kJ/kg (b) -810 kJ/kg (c) -708.5 kJ/kg (d) -810 kJ/kg

A steam engine isentropically expands 7.382 kg/sec of steam from 0.68 Mpa,

220°C, the exhaust is dry and saturated. Determine (a) the work of nonflow

process in kW and (b) the work of a steady flow process in kW. NOTE: - INDICATE THE HS and TS DIAGRAM - INDICATE THE INITIAL AND FINAL STATE OF THE SUBSTANCE

Water at 2.5 MPa and 200°C is heated at constant temperature up to a quality of 80%. Find (a) the quantity of heat received by the water, (b) the change in internal energy, and (c) the work of a nonflow process. NOTE: - INDICATE THE HS and TS DIAGRAM - INDICATE THE INITIAL AND FINAL STATE OF THE SUBSTANCE

Ans. (a) 2025.7 kJ/kg; (b) 1396.5 kJ/kg; (c) 629.17 kJ/kg

6.371 kg of water vapour are contained at 150 kPa ad 90 per cent quality in a

suitable enclosure. Calculate the heat which must be added in order to just

produce a saturated vapor. What will the pressure be at the end of the

heating process? NOTE: - INDICATE THE HS and TS DIAGRAM - INDICATE THE INITIAL AND FINAL STATE OF THE SUBSTANCE

6.86 kg of water vapour are contained at 150 kPa ad 90 per cent quality in a

suitable enclosure. Calculate the heat which must be added in order to just

produce a saturated vapor. What will the pressure be at the end of the

heating process? NOTE: - INDICATE THE HS and TS DIAGRAM - INDICATE THE INITIAL AND FINAL STATE OF THE SUBSTANCE

6.86 kg of water vapor are contained at 150 kPa ad 90 percent quality in a

suitable enclosure. Calculate the heat in kJ which must be added in order to just

produce a saturated vapor. NOTE: - INDICATE THE HS and TS DIAGRAM - INDICATE THE INITIAL AND FINAL STATE OF THE SUBSTANCE

A piston cylinder containing steam at 700 kPa at 250 degrees celcius undergoes a constant pressure process until the quality is 70%. Determine: a). Work done b). Heat transferred c). Change in internal energy d). Change in enthalpy NOTE: - INDICATE THE HS and TS DIAGRAM - INDICATE THE INITIAL AND FINAL STATE OF THE SUBSTANCE

a welded joint, as shown in fig. is subjected to an eccentric load of 2500 n. find the size of the weld, if the maximum shear stress in the weld is not to exceed 50 n/mm^2

A plate 60 mm wide and 12.5 mm thick is to be welded to another plate by means of parallel fillet welds. The plates are subjected to a load of 80 kN. Find the length of the weld. Assume allowable shear strength to be 60 MPa.