Mechanical Engineering Principles

212 MECHANICAL ENGINEERING PRINCIPLES Thus, for example, 0°C=273 K, 25°C=298 K and 100°C=373 K Problem 1. Convert the following ...

HEAT ENERGY AND TRANSFER 213 Problem 3. Calculate the quantity of heat required to raise the temperature of 5 kg of water from 0 ...

214 MECHANICAL ENGINEERING PRINCIPLES Quantity of heat required for the water is given by: QW=mc(t 2 −t 1 ) =(1kg) ( 4. 2 kg kg ...

HEAT ENERGY AND TRANSFER 215 changes are reversible processes. When heat energy flows to or from a substance and causes a change ...

216 MECHANICAL ENGINEERING PRINCIPLES Table 19.1 Latent heat of Melting fusion (kJ/kg) point (°C) Mercury 11.8 − 39 Lead 22 327 ...

HEAT ENERGY AND TRANSFER 217 (ii) Latent heat needed to change ice at 0°Cinto water at 0°C is given by: Q 2 =mLf= 0 .4kg×335 kJ/ ...

218 MECHANICAL ENGINEERING PRINCIPLES (ii) The metal of a radiator of a central heating system conducts heat from the hot water ...

HEAT ENERGY AND TRANSFER 219 (i) Since convection causes hot air to rise it is important to insulate the roof space, which is pr ...

220 MECHANICAL ENGINEERING PRINCIPLES (a) 500 kJ (b) 0.5 kJ (c) 2 J (d) 250 kJ The heat energy required to change 1 kg of a sub ...

20 Thermal expansion At the end of this chapter you should be able to: appreciate that expansion and contraction occurs with ch ...

222 MECHANICAL ENGINEERING PRINCIPLES different strips of metal riveted together). When heated, brass expands more than steel, a ...

THERMAL EXPANSION 223 In practice, allowances are made for such expan- sions.U-shaped expansion joints are connected into pipeli ...

224 MECHANICAL ENGINEERING PRINCIPLES of the hot pipe if the coefficient of linear expansion of lead is 29× 10 −^6 K−^1. [50.092 ...

THERMAL EXPANSION 225 20.6 Coefficient of cubic expansion The amount by which unit volume of a mate- rial increases for a one de ...

226 MECHANICAL ENGINEERING PRINCIPLES Hence increase in surface area = 2500 π( 0. 018 )= 141 .4mm^2 (c) Initial volume of sphere ...

THERMAL EXPANSION 227 (b) Initial volume of glass, V 1 = 100 × 50 × 20 =100 000 mm^3 Final volume of glass, V 2 =V 1 [1+γ(t 2 −t ...

228 MECHANICAL ENGINEERING PRINCIPLES Exercise 105 Multi-choice questions on thermal expansion (Answers on page 285) When the t ...

THERMAL EXPANSION 229 Assignment 6 This assignment covers the material con- tained in chapters 19 and 20. The marks for each que ...

21 Hydrostatics 21.1 Pressure The pressure acting on a surface is defined as the perpendicular force per unit area of surface. T ...

HYDROSTATICS 231 Now try the following exercise Exercise 106 Further problems on pres- sure A force of 280 N is applied to a pi ...