refrigerants: $R-143$a $(1,1,1-$trifluoroethane$)$ at $52$ mass $\%,$

R$-125($pentafluoroethane$),$ at $44$ mass $\%,$ and the

balance R$-134$a $(1,1,1,2-$tetrafluoroethane$).$

For the warehouse in question, you expect that the

system will need to provide $100kW$ of cooling to the

refrigerated space at peak operation in order to maintain

it at an average temperature of $-18C.$

Heat is rejected to the surrounding air, which may be up

to $36C$ on a hot summer day $($peak operation$).$ This is

accomplished using an air$-$based exchanger as well. For

an air$-$based cooler such as this, a $10C$ approach

temperature is a good guideline for your design

calculations.

There are four devices used in this refrigeration cycle:

A compressor pressurizes a stream of refrigerant

vapor, which moves on to$...$

A condenser, which rejects heat to the outside air

while creating a high$-$pressure stream of refrigerant

liquid. This liquid is then expanded across...

A valve adiabatically, which produces a very cold,

mixed liquid$-$vapor stream of refrigerant that moves

along to$...$

An evaporator, which extracts heat from the

refrigerated space as the refrigerant boils, cooling

the air inside.

Answer the following $-$ and note, Aspen is not required

for all of these.

$($a$)$ Using the tables in the file $"$R$404$A$\_$SI$.$pdf$"$ on Canvas,

what should the absolute pressure $($in kPa $)$ of the

refrigerant entering the evaporator be$,$ assuming you

would like it to be maintained at the refrigerated space's

average temperature $)$ as it evaporates $($use $P_f,$ as it

starts out as mostly liquid$)?$

$($b$)$ Using the tables in the file $"$R$404$A$\_$SI$.$pdf$"$ on Canvas

and the conditions specified in $($a$),$ find the pressure $($in

kilopascals$)$ of the vapor entering the compressor,

assuming it is a saturated vapor $($use $P_F).$

$($c$)$ What should the temperature $($in $C)$ of the refrigerant

leaving the condenser be$,$ assuming a $10C$ approach?

NOTE: The $10C$ approach temperature design

assumption, which is used to determine a system

pressure using the tables, is not necessary for your HeatX

block in your simulation.

$($d$)$ Using the tables in the file $"$R$404$A$\_$SI$.$pdf$"$ on Canvas

and the temperature specified in $($c$),$ find the pressure $($in

kilopascals$)$ of the liquid leaving the condenser, assuming

it is a saturated liquid $($use $P_f).$

$($e$)$ Build a flowsheet for this system in Aspen Plus,

including all work, refrigerant, and air streams. Make

sure to use HeatX for the condenser, rather than two

paired heaters. Include an image of the complete

flowsheet in your submission.

NOTE: The $10\backslash$deg C approach temperature design

assumption, which is used to determine a system

pressure using the tables, is not necessary for your HeatX

block in your simulation.

Assuming$/$using the following, and using the REFPROP

thermodynamic method,

$$ A low refrigerant system pressure from $($a$)$

$$ A high refrigerant system pressure from $($d$)$

$$ Isentropic compressor functions at $75\%$ efficiency

$$ Saturated liquid refrigerant leaving the condenser

$$ Saturated vapor refrigerant leaving the evaporator

at the pressure from $($b$)$

$$ Countercurrent operation of heat exchangers

$$ No pressure loss across the condenser

$$ Outdoor air $(78\%$ N$2,21\%$ O$2,1\%$ Ar$)$ stream to be at

$100$ kPa absolute pressure

$($f$)$ Find the maximum circulation rate, $($in kmol$/$hr$)$ of

refrigerant required to withdraw enough heat $(100$ kW of

NET$-$DUTY$)$ from the chilled space inside the warehouse.

$($g$)$ You are uncertain that the $75\%$ specified isentropic

efficiency $($SEFF$)$ for the compressor has been accurately

quoted. Perform a Sensitivity analysis to determine the

effect of the compressor$$s isentropic efficiency $($from

$55\%$ to $90\%$ by $1\%$ increments$)$ on its indicated power

$($IND$-$POWER$),$ in kW$.$ Display a plot with your submission.