QUESTION $1$

An engine is operating on the Carnot cycle between temperatures $1073$K and $407$K

and maximum and minimum pressures of $230$ bar and $2\mathrm{.}07$ bar respectively.

Calculate:

$1\mathrm{.}1.$ Thermal efficiency. $(3)$

$1\mathrm{.}2.$ Isothermal expansion ratio. $(5)$

$1\mathrm{.}3.$ Net work done. $(9)$

$1\mathrm{.}4.$ Work ratio. $(4)$

Take the working fluid as air and use $=1\mathrm{.}3$ and Cp $=1\mathrm{.}005$ kJ$/$kg$.$K

$[21$ marks$]$

QUESTION $2$

Find the specific work done in a Rankine cycle if the steam supplied at $650$ kPa and

$0\mathrm{.}9$ dry and the condenser pressure is $30$ kPa. Assume that the expansion of the steam

follows PV$1\mathrm{.}6=$ constant. $(12)$

$[12$ marks$]$

QUESTION $3$

Feed water enters a boiler at $30$oC$.$ Steam leaves the boiler $95\%$ dry at a pressure of

$2600$ KPa and passes through a super$-$heater where its temperature is raised to $260$oC

at constant pressure. The steam output is $8\mathrm{.}5$ kg of coal burnt. The coal has a calorific

value of $50$ MJ$/$kg$,$ calculate

$3\mathrm{.}1.$ The plant efficiency. $(7)$

$3\mathrm{.}2.$ The equivalent evaporation from and at $100$oC$.(3)$

$3\mathrm{.}3.$ The heat transfer rate per kg of coal in the evaporator and in the superheater.

$(3)$

$[13$ marks$]$

TDA$3701$ Minor Test $022024$

$3$

QUESTION $4$

A CO$2$ refrigeration unit works between the temperature limits of $-25\backslash$deg C and

$10\backslash$deg C$.$Calculate the following:

$4\mathrm{.}1.$ Ideal coefficient of performance. $(3)$

$4\mathrm{.}2.$ The mass of ice the unit can produce in two hours if it uses water at $16\backslash$deg C$,$ the

relative COP is $0\mathrm{.}70$ LI for ice is $330$ kJ$/$kg and the power supplied is $100$ kW$.$

$(9)$