Why Are All The States For R-22, Ammonia And R. 134a?
Results
The temperature of the hot and cold reservoirs are known to be 40℃ and 2℃, and that the temperature difference between hot reservoir and the evaporator, and cold reservoir and condenser is 20℃, therefore using the equations 1 and 2, the evaporator temperature is 60℃ and the condenser temperature is -18℃. Using the procedure described in the Methods section, Thermostate and equation 3 can be applied to find the all the states for R-22, Ammonia and R-134A, as tabulated below:
Using equations 4 and 5 for all three working fluids, the mass rates for R-22, Ammonia and R-134A are evaluated to be 2.339 kg/min, 0.29665 kg/min and 2.806 kg/min respectively; with Ammonia having the lowest flow rate and R-134A as the highest. This is because …show more content…
Despite the Ammonia having the lowest mass flow rate, the system still has highest coefficient of performance; hence proving that there is no correlation between mass flow rate and the coefficient of performance. These coefficients, however, are way below the maximum coefficient of performance of a Carnot cycle operating at T_c and T_H, which can be found using equation 8. The Carnot efficiency of the cycle is evaluated to be 8.24; almost 5 times as much as the efficiency using Ammonia as the working fluid. The reason why there is such a difference between the two cycles is because there is temperature difference between the cold reservoir and evaporator, and the hot reservoir and condenser. This creates irreversibilities and hence the coefficient of performance is lower when this temperature difference (between the cold reservoir and evaporator, and the hot reservoir and condenser) is …show more content…
The rate of entropy production is 0.08945 kW/K for R-22, 0.06403 kW/K for Ammonia and 0.10359 kW/K for R-134A. The closer the rate of entropy production is to zero, the more the process is closer to being irreversible, as with Ammonia in this case. This is desirable as there is not much entropy or energy lost during the compression of the fluid between state 1 and state 2.
To be able to calculate the cost of operating the refrigeration cycle using these fluid, we first need to calculate the compressor work using equation 10. The larger the compressor work is, the more electricity the compressor is drawing. We can multiply the number of kilowatts to the number of hours electricity will be used in a month to calculate the number of kilowatt hours, i.e. 720 hours assuming a 30 day month. Using equation 11, the number of kilowatt hours used by R-22, Ammonia and R-134A are 121366.65 kWh, 108554.5 kWh and 129761.65 kWh respectively.
Since all three cycles are using way more than 250 kWh, a flat rate of 250 kWh * 15.225 cents/kWh can be applied to all three cycles, which totals $38.06. The remaining cost can be calculated using equation 12 by multiplying the remaining number of kilowatt hours to a rate of 18.286 cents/kWh. The total cost of using R-22, Ammonia and R-134A is $22185.45, $19842.62 and $23720.56 respectively, with Ammonia being the cheapest
The temperature of the hot and cold reservoirs are known to be 40℃ and 2℃, and that the temperature difference between hot reservoir and the evaporator, and cold reservoir and condenser is 20℃, therefore using the equations 1 and 2, the evaporator temperature is 60℃ and the condenser temperature is -18℃. Using the procedure described in the Methods section, Thermostate and equation 3 can be applied to find the all the states for R-22, Ammonia and R-134A, as tabulated below:
Using equations 4 and 5 for all three working fluids, the mass rates for R-22, Ammonia and R-134A are evaluated to be 2.339 kg/min, 0.29665 kg/min and 2.806 kg/min respectively; with Ammonia having the lowest flow rate and R-134A as the highest. This is because …show more content…
Despite the Ammonia having the lowest mass flow rate, the system still has highest coefficient of performance; hence proving that there is no correlation between mass flow rate and the coefficient of performance. These coefficients, however, are way below the maximum coefficient of performance of a Carnot cycle operating at T_c and T_H, which can be found using equation 8. The Carnot efficiency of the cycle is evaluated to be 8.24; almost 5 times as much as the efficiency using Ammonia as the working fluid. The reason why there is such a difference between the two cycles is because there is temperature difference between the cold reservoir and evaporator, and the hot reservoir and condenser. This creates irreversibilities and hence the coefficient of performance is lower when this temperature difference (between the cold reservoir and evaporator, and the hot reservoir and condenser) is …show more content…
The rate of entropy production is 0.08945 kW/K for R-22, 0.06403 kW/K for Ammonia and 0.10359 kW/K for R-134A. The closer the rate of entropy production is to zero, the more the process is closer to being irreversible, as with Ammonia in this case. This is desirable as there is not much entropy or energy lost during the compression of the fluid between state 1 and state 2.
To be able to calculate the cost of operating the refrigeration cycle using these fluid, we first need to calculate the compressor work using equation 10. The larger the compressor work is, the more electricity the compressor is drawing. We can multiply the number of kilowatts to the number of hours electricity will be used in a month to calculate the number of kilowatt hours, i.e. 720 hours assuming a 30 day month. Using equation 11, the number of kilowatt hours used by R-22, Ammonia and R-134A are 121366.65 kWh, 108554.5 kWh and 129761.65 kWh respectively.
Since all three cycles are using way more than 250 kWh, a flat rate of 250 kWh * 15.225 cents/kWh can be applied to all three cycles, which totals $38.06. The remaining cost can be calculated using equation 12 by multiplying the remaining number of kilowatt hours to a rate of 18.286 cents/kWh. The total cost of using R-22, Ammonia and R-134A is $22185.45, $19842.62 and $23720.56 respectively, with Ammonia being the cheapest