1. Thermo-physical properties 2. Radiation properties - nptel - Indian ...

Mechanical Measurements Prof S.P.Venkatesan
Indian Institute of Technology Madras
continuous flow of the gas air mixture (air provides oxygen for combustion) and
the coolant (water) through the cooling coils. As indicated temperatures and flow
rates are measured using appropriate devices familiar to us from Module 2. The
gas air mixture is burnt as it issues through a nozzle that is surrounded by a
cooling coil through which a continuous flow of cooling water is maintained. The
enthalpy fluxes involved in the apparatus are given below:
1) Gas air mixture (mg) entering in at room temperature (Tg,entry)
Mass flow measured using venturi
Temperature measured using a liquid in glass thermometer
2) Products of combustion leaving at a higher temperature (Tg,exit)
Temperature measured using a liquid in glass thermometer
3) Cooling water (mw)entering at constant temperature (Tw,entry)
Mass flow measured by rotameter
4) Cooling water stream leaves at a higher temperature (Tw,exit)
Temperature measured using a liquid in glass thermometer
Energy balance requires that the following hold:
( )
mHV= C T − C T + m C T − T
(14)
g pp g,exit pm g,entry w pw w,exit w,entry
In the above equation HV is the heating value of the fuel, Cpp is the specific heat
of products of combustion and Cpm is the specific heat of gas air mixture. The
determination of Cpp will certainly require knowledge of the composition of the
products formed during the combustion process. The products of combustion
have to be obtained by methods that we shall describe later. In the case of