MarksA1
From measurements taken at two points on the compression curve of an oil engine indicator diagram, as shown, the following data are recorded:①pressure 140 kN/m², volume 12 litres②pressure 2·8 MN/m², volume 1·2 litres
(a)Determine the polytropic index, n, for the curve between the two points and, hence:
3(b)Calculate the work done between the two points.
4(c)Assuming a temperature of 100°C at the first point, determine the temperature at the second point.3Take J/kgK717·0,kJ/kgK287·0
The temperature of a gas streamis to be measured by a thermocouple whose junction can be approximated to a 1·2 mm-diameter sphere. The properties of the junction are:J/kgK,320andkg/m8500,W/mK353pCk.
The heat transfer coefficient between the junction and the gas is W/m²K65h10
Determine how long it will take for the thermocouple to read 99% of the initial temperature difference.
Consider two identical bodies, one at 5000 K and the other at 2000 K. With the aid of a suitable diagram, explain:
(a)Which of the two bodies will emit more radiation in the shorter-wavelength region.
8(b)Which of the two bodies will emit more radiation at a wavelength of 20 μm.2
Section A continues on the next page.PV①②
QA4.Figure QA4Oil of density 780 kg/m3flows from A to B at the rate of 375 litre/s. The level of B is 4.5m higher than that of A. The pipeline at A has an internal diameter of 300 mm; at B the internal diameter is 600mm. The gauge pressure at A is 50 kPa.
Assume that there is no loss ofenergy from A to B.
(i)Determine the pressure at B.6
(ii)Determine the velocity heads and pressure heads at A and B, and from those determine the total energy heads at A and at B, taking the datum level (of zero energy) as at 3m below point A
