The answer is option e (i.e both a and b). Heat capacity Cp (kJ/Kg.K) is functio

Question

The answer is option e (i.e both a and b).

Heat capacity Cp (kJ/Kg.K) is function of Temperature and pressure, hence to calculate the average heat capacity,

option a is appropriate. Similar is the case for calculation of Density which is also function of temperature and pressure.

The option c is in appropriate as their is no phase change, hence we need not to consider the term (hg) as it is the enthalpy of gas, and here the oil does not undergo phase change.

Part 2:

The option d is correct, (all a,b, c are relevant). The same logic is applied for options a and b as in the case of oil.

But as mentioned in the question the output stage of water is steam, we have to consider the enthalpy change associated with the gas (in this case steam), hence option c is also relevant."

My convoluted thoughts about a and b on the water:
I thought about this for a second, and I am agreement with them on the oil. However, the water goes through a phase change, and I googled specific heat of water liquid and vapor... and their quite different... like 1 and 4... and density would be even worse... 1000 kg/m3 for water liquid and 0.554kg/m3 for water vapor... and the water comes out at 100C wich means it just turned to a gas, causing the value of the water's density to just dive when it leaves... so just going off my knowledge of statistics, averages can be really influenced by outliers.... I'm just imagining like the density and Cp averages being REALLY skewed... and that they wouldn't represent the system... unless if you really can just average them for an approximation... (It really seems like this class and topic just butchered right and left just for the sake of an idea...)

It's really long... and i'm prolly over thinking this... but I hope you understand my train of thought

Please check for comments I leave tomorrow, as I might leave follow up questions on your explanation or I'll say that I am good, for a thumbs up.

A thin-wall, double-pipe, counter flow heat exchanger is used to cool oil from Te oil to T oil The volume in out flow rate (Voil), density (poil), capacity the oil oil are known. Ice water of a known volume and heat of (C flow rate (Vh20) is used to cool the oil in the heat exchanger, where the output is actually a 100% saturated steam at (100°C, 1 atm). In the expressions below, the subscripts 1 and 2 correspond to input (in and output (out), respectively What expressions are valid for describing the input and output properties of the oil? [5 S. oil oil (ah/OT) cp @T2, P2)loill (a) oil (b) poil 1, P1)loil oil oil ha T2, P2) (c) 1, r 1 oil oil (d) (a, b, and c) (e) (a and b) What expressions are valid for describing the input and output properties of the water? [5 pts.] h o 1 h o lcp (OT1, ice-water cp 2, P2) sat steam]; Cp (a) (dh/OT) (b) ph2o 1, Pa)lice 2, P sat, steam] ice-water (c) h o hf (@T1, P1) ice-water hh20 ha T2, P2) sat. Steam (d) a, b, and c) (a and b) (e)

Explanation / Answer

Part 1.

The answer is option e (i.e both a and b).

Heat capacity Cp (kJ/Kg.K) is function of Temperature and pressure, hence to calculate the average heat capacity,

option a is appropriate. Similar is the case for calculation of Density which is also function of temperature and pressure.

The option c is in appropriate as their is no phase change, hence we need not to consider the term (hg) as it is the enthalpy of gas, and here the oil does not undergo phase change.

Part 2:

The option d is correct, (all a,b, c are relevant). The same logic is applied for options a and b as in the case of oil.

But as mentioned in the question the output stage of water is steam, we have to consider the enthalpy change associated with the gas (in this case steam), hence option c is also relevant."

thumbs up for your thinking..great

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