代写MAE 115 Applied Engineering Thermodynamics 2023 Examination #3代做Python编程

日期：2024-08-22 06:26

MAE 115 – Applied Engineering Thermodynamics

Examination #3

2023

Conceptual Short Answer (30 points):

1.   Answer the following questions as concisely as possible:

a)   You must design a heat pump system capable of creating steam at 1 atm. Circle or highlight which working fluid you would examine first for use in your heat pump.

Refrigerant Name	Critical Temperature (oF)	Critical Pressure (PSIa)	Global Warming Potential (CO2 molecules/refrigerant molecules)
R-1336mzz(Z)	336	420	2
R-717	270	1643	0
R1243zf	218.804	510.2055295	0
R-134a	214	589	1430
R410A	160.4192	710.8339376	2088

b)   In certain warm, humid areas, it will rain every day shortly after the sun goes down. Why?

c)    When considering the pairing a topping cycle with a bottoming cycle to form a combined cycle, what is the first aspect that should be considered?

d)   In a standard vapor-compression refrigeration system, why do we use a throttling valve in place of a turbine?

e)   In a gas refrigeration cycle, why do we use a turbine instead of a throttling valve?

f)   In a refrigeration cycle, what is the purpose of a regenerator? Does the addition of a regenerator boost system COP?

Combined Cycle (20 points):

2.   A gas turbine – steam turbine combined cycle operates at the state points defined in the table and

diagram below. If the combined cycle produces 100 MW, determine a) mass flow rates of water and air, and b) the system thermal efficiency. Assume constant specific heat in the gas cycle using a Cp=1.005 kJ/kg*K.

Steam Turbine		Gas Turbine
State	h (kJ/kg)	State	T (K)
1	251	5	293
2	258	6	570
3	2950	7	1400
4	2030	8	760
		9	550

Refrigeration (25 points):

3.   A refrigeration cycle is used to 18 kW refrigeration for a living space during the summer.

The working fluid is Refrigerant 134a, and the pressures of the evaporator and condenser are 20 and 100 psia respectively.

Note:You do not need to interpolate. Instead, take the average of the two closest values in a table.

Determine the following:

(a) Plot the T-s diagram for the refrigeration process (b) Complete the table below

(c) Calculate the mass flow of the Refrigerant 134a in lbm/min

(d) Determine the work and heat energy transfers and appropriate sign (+ or -) in Btu/min for all processes.

(e) Calculate the coefficient of performance (COP)

(Extra credit): Considering a practical system with practical heat exchangers, what is the minimum interior and maximum exterior temperature that can be maintained using this system?

State Point	T (oF)	h (Btu/lbm)
1
2
3
4

Psychrometrics(25 points):

4.   Outdoor air at 1 atm is at 40oC and 50% relative humidity. Indoor air is to be kept at 22oC and 40% relative humidity.

Determine the following:

a)  Fill out the table below for the outdoor and indoor air thermodynamic properties.

b)  Clearly state the name and order of the processes required to move from the outdoor air properties to indoor air.

c)  Plot all thermodynamic processes required on the attached psychrometric chart.

d)  For a mass flow rate of 10 kgdry air per second, calculate the total heat transfers and water mass flow rates into and out of the air

(Extra Credit) If the cooling and dehumidification process is accomplished through the use  of a vapor compression chiller system, and there is an absolute difference of 5oC between the air leaving the chiller and evaporator, and an absolute difference of 5oC between the 40oC outside air and condenser, what are the temperatures at which the evaporator and condenser are operating?

Property	Outdoor Air	Indoor Air
Wet Bulb Temperature (Co)
Dew Point (Co)
Specific Enthalpy (kJ/kgdry air)
Absolute humidity (gH2O/kgdry air)
Specific volume (m3/kgdry air)

Enthalpy of Saturated Liquid Water
Temperature (oC)	H (kJ/kg)
0.01	0.001
5	21.020
10	42.022
15	62.982
20	83.915
25	104.83
30	125.74
35	146.64
40	167.53
45	188.44

Extra Credit - Air Conditioning Processes + Favorite Subject (13 points)

Draw an example of the specified air conditioning process on the simplified psychrometric charts. Label all states using numbers using “ 1” as the initial state. Use arrows to indicate process directions.

Evaporative Cooling	Humidification Using Superheated Steam
Cooling and Dehumidification with Reheat	Adiabatic Mixing of Two Inlet Air Streams (stream 1 & 2) into a Single Outlet Air Steam (stream 3)

What was your favorite subject from the class? Why?