A cold room complex is built at a coastal location where the design conditions are $35$C DB; $22$C WB$.$ The complex is served by a dual$-$pressure, DX$,$ Ammonia $($R$717)$ system which employs intercooling and flash gas removal. The complex consists of two equally sized rectangular rooms, sharing one common wall, and forming a $30$m x $30$m square with a height of $6$m$.$ One of the rooms is a frozen store facility of which the total load is $200$kW including the runtime factor and the safety factor.$$ This store is kept at $25$C and the blower$-$coil unit operates at $30$C$.$ The adjoining store is a chilled store suitable for handling $20$tonnes of mixed fresh vegetables per $24-$hour period from an entering temperature of $25$C$.$ A $4$kW electric forklift truck is used to carry vegetables in and out of the chilled store.$$ Six people work an $8-$hour shift inside the chilled store. The complex is built on the ground and all walls are constructed of $125$mm thick, steel clad, polystyrene sandwich panels.$$ The roof is flat and painted light blue.$$ The roof and floor construction have the same overall heat transfer coefficient as the walls and all walls are shielded from the sun except the long wall of the chilled store, which faces East and is painted a light blue colour.

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The chilled store has two blower$-$coil units, each with two fans, driven by $1,5$ kW motors.

The plant has a water$-$cooled condenser which is served by a cooling tower with an approach of $6$C and a range of $5$C$.$

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$$ General plant particulars and assumptions.

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Allow for $10$C of liquid Ammonia subcooling in the condenser.

For the rest of the plant, saturated conditions can be used where necessary.

The blower$-$coil units of the vegetable room and the intercooler surge drum operate at the same pressure.

The compression in all the compressors can be assumed to be isentropic$.$

The compressors have a mechanical efficiency of $85\%.$

The condenser cooling water outlet temperature is $2$C less than the condensing temperature.

A safety factor of $10\%$ and a runtime factor of $18$ hours must be used for all capacity calculations.

A defrost load of $1500$W is applied over a four hour period.

Neat block diagrams showing the essential pipework and P$-$h diagrams are essential.

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$$ REQUIREMENTS.

$$ The following calculations must be submitted:

$($i$)$ The required refrigerating capacity of the vegetable room to satisfy the client.

$($ii$)$ The total power to drive the plant and the C$.$O$.$P$.$R based on the power to drive the plant.

$($iii$)$ The required flow rate of cooling water through the condenser.