NT3036 LABORATORY REPORT AIR CONDITIONING PROCESSES

School of Engineering
UCLan Coursework Assessment Brief
20/21
Module Title: Systems Design Module Code: NT3036
Level 6
LABORATORY REPORT
AIR CONDITIONING PROCESSES
This assessment is worth 50% of the overall module mark
THE BRIEF/INSTRUCTIONS
Objectives
1. To measure the steady state air conditions across a number of air conditioning plant items and to plot the psychometric cycle.
2. To perform energy and moisture balances on appropriate plant items.
Apparatus
A diagram of the apparatus is attached in Fig. 1 and the photo of the apparatus is attached in Fig. 2.
1. Air Movement
Air is expelled into the room through an orifice plate which is used to measure the total air flow rate.
2. Electric heater battery
Heaters are separately switched providing several levels of heat input.
3. Steam humidifier
Steam is generated by separately switched electric heaters, allowing for varied steam injection into the system. The humidifier has its own small water feed tank.
4. Cooler coil and refrigeration plant
The direct expansion refrigeration system incorporates an automatic expansion valve which ensures a constant evaporator presser The refrigerant is circulated through the evaporator and leaves in a saturated condition ensuring that no significant changes of temperature occurs . This reduces the tendency for the air to leave the cooler with a significant temperature gradient across the duct. The saturated vapour leaving the evaporator passes into the compressor. The refrigerant leaving the compressor circulates through the condenser and then into a liquid receiver and back to the expansion valve.
The nominal rate of the refrigeration can be found on the compressor plate among with Full Load amps and Locked Rota (FLA LRA) voltage etc.
5. Droplet elimination
Any moisture carried as droplets in the air is caught by the spray (droplet) elimination device, located downstream of the cooling coil. The condensation is drained from the coil and from the eliminator.
6. Supply fan and discharge
The centrifugal supply fan handles the total flow and through the apparatus. The fan speed is adjustable in order to accommodate varied volume flow rate.
Static pressure tapings are installed on the discharge duct.
7. Temperature measurements.
Thermocouples are installed at the several positions along the apparatus ductwork for dry bulb and wet bulb temperature measurements.
Method & Procedure
1. Air conditioning
1a. Method
The fan and air conditioning plant are to be left to run in a steady state mode.
The pressure differences of the orifice plate to be registered at the beginning, mid-way and at the end of the temperature measurements.
Log the temperature through the apparatus at 5min. intervals for a period of approximately one hour.
Record the electrical energy inputs of the heater and humidifier (boiler).
Collect and weigh the condensate of the cooling coil over the period of the temperature measurements. (Insure that steady state conditions prevail and that all condensate is collected).
Record the barometric pressure. (Pb.)
1b. Procedure
1. Make sure that the air conditioning (A/C) unit is connected up to a computer (with a printer) via a RS232 port and check that all water reservoirs for wet bulb sensors are filled with distilled water.
2. Switch on the isolator and start the A/C unit by turning on the main switch on the control panel.
3. Turn on the computer and boot it up in DOS mode with the formatted disc in drive A.
4. Type RUN <return> to start the program.
5. Type CHAIN “574COLC” in capital letters <return>.
6. Press N in response to the displayed question that data are to be obtained from the A/C unit.
7. Press N in response to the displayed question that data are to be saved onto a floppy disc unless it is so desired.
8. Check that the computer and the A/C unit are in communication by observing 4 audible beeps and flashings of the Interface Status lamp on the control panel.
9. Enter the refrigerant flow meter calibration factor, the atmospheric pressure in mm Hg and the heater resistances into the computer. The required data, except the atmospheric pressure, can be found on the data sheet adhered on the control panel. The atmospheric pressure can be obtained from the wall-mount barometer in the laboratory.
10. The set up should be ready for use after the required information is input. Select option 2 to display the psychrometric chart with the A/C cycle plotted.
11. Do NOT print out any data until the system is steady and when they are needed.
12. Turn the fan speed control to give a moderate flow.
13. Start the compressor.
14. Turn on the water supply ball valve to supply make-up water to the boiler. THE WATER LEVEL IN THE BOILER HAS TO BE CONTINUOUSLY MONITORED TO ENSURE THAT IT IS MAINTAINED BETWEEN THE TWO RED LINES MARKED ON THE SIGHT GLASS TO AVOID OVERFLOW OR DRYING UP LEADING TO BURING OF HEATERS. If necessary, make use of the ball valve to control the water level.
15. Energise the 2 kW water heater and the 1 kW after-heater and allow the system to become steady.
16. The cycle on the display will be updated in 1-minute intervals with momentarily lighting up of the
system sampling lamp on the control panel. Only the latest two cycles will be shown with the second last one presented in dotted lines. The appearance of a single plot indicates that the system is steady.
17. Press R to return the display to the Master Menu after the system is steady. Select option 2 and input Y to print out the data.
18. Press R and selection option 2 with input of N to stop further printing after the required printout is obtained.
19. Obtain the rate of condensation by measuring with a beaker a required quantity of condensate from the evaporator in a certain duration.
20. Measure the temperatures of room air, make-up water from a tap and condensate.
21. The 2 kW water heaters and 1 kW after-heaters maintained turning on and 2 kW pre-heaters are then turned on.
22. The measurement of the temperature is carried out through the apparatus at 5 minute intervals for a period of approximately 1 hour.
23. The collection of the weight of the condensate of the cooling coil over the period of the temperature measurements (Insure that steady state conditions prevail and that all condensate is collected).
24. At the end of the test, open all switches for the heaters and compressor.
25. Allow the fan to run for at least 5 minutes to dissipate any residual energy.
26. Switch off the power supply on the control panel and turn off the isolator.
27. Turn off the water supply ball valve.
28. Return the computer display to the master menu and select option 5 to close all files and quit to DOS.
29. Switch off the computer and the printer.
2. Refrigeration
2a. Method & procedure
During the measurement of the air-conditioning process, the readings of the refrigeration system need to be simultaneously recorded both of pressures (Evaporator Plow and Condenser Phigh) and temperatures (Evaporator t12 & t9, Condenser t10 and TEV inlet t11).
Reading of refrigerant flow and compressor running amps every 5 minutes will also assist in the energy balance of the apparatus.
Please note that Insuring steady state has been obtained before reading commence.
Theoretical Background
1. Humidifier (Boiler)
Heat loss rate from Humidifer(boiler) (Qb,l) = 0.0043 x temperature difference between steam and room air, kW
Rate of evaporation at boiler (mw,b) = (Humidifier(Boiler) heat input rate Qb,s – Qb,l)/2501, kg/s
2. Energy and mass balance between A and B
Rate of moisture addition to air (mw,a) = ma (wB – wA), kg/s
Energy input rate (Q) = Qb,s + Qp + Wfan + Qw, kW
Rate of energy gained by air (H) = ma (hB – hA), kW
where ma = mass flow rate of air, kg/s
w = moisture content of air, kg/kg
h = specific enthaply of air, kJ/kg
Qp = energy input rate at pre-heaters, kW
Wfan = fan power input = 0.072 kW
Qw = energy input rate of humidifier (make-up water) = mw,a x 4.18 x tw, kW
tw = temperature of make-up water, ºC
Percentage difference between moisture generation at Humidifier(boiler) and moisture absorption by air (%m) = 100 [(mw,b – mw,a)/mw,b], %
Percentage difference between energy input and energy gained by air (%A-B)
= 100 [(Q – H)/Q], %
3. Energy and mass balance between B and C
Rate of moisture removal from air (mw,c) = ma (wB – wC), kg/s
Rate of heat gain from room air (QB-C) = ma (hC – hB) + mw,c hcond + Qcc, kW
where hcond = specific enthaply of condensate = 4.18 x tcond, kJ/kg
tcond = temperature of condensate, ºC
Qcc = rate of energy removal at evaporator = mr (h1 – h4), kW
mr = mass flow rate of refrigerant R134a, kg/s
h1 = specific enthalpy of refrigerant leaving evaporator, kJ/kg
h4 = specific enthalpy of refrigerant entering evaporator = h3, kJ/kg
Percentage difference between measured rate of condensation and rate of moisture removal from air (%cond) = 100 [(mcond – mw,c)/mcond], %
where mcond = measured rate of condensation, kg/s
4. Energy balance between C and D
Rate of energy gained by air (QC-D) = ma (hD – hC), kW
Percentage difference between rate of energy input at after-heaters and rate of energy gained by air (%C-D) = 100 [(Qa –QC-D)/Qa], %
where Qa = rate of input at after-heaters, kW
5, Air density
Air density = 1.2 x ((Pb.)/1013.2) x (293/273+t) Kg/m3
Results and calculation
1. To calculate the air volume flow rate and the diameter orifice plate are required.
2. Air Conditions
a. Plot the temperature against time and tabulate the following properties for each change of air condition as shown in Appendix A.
• Dry bulb temperature
• Wet bulb temperature (sling)
• Dew-point temperature
• Enthalpy
• Moisture content
• Specific volume.
b. Plot the complete “air conditioning” cycle on a psychometric chart (for both conditions).
(Note that to plot a cycle that “works” some air conditioning may have to be modified by calculations from the energy and mass balance).
3. Monitor the refrigeration system and its energy exchange.
4. Tabulate finding as with the air conditioning results as shown in Appendix A.
5. Plot refrigeration cycle on a Pressure Enthalpy chart.
Analysis & Conclusions
Comment on the influence of the heat exchanger on the refrigeration cycle and suggest reasons for its use.
Comment on the operation of the Thermal Expansion Valve (TEV) to regulate the flow of refrigerant through the evaporator.
Energy and moisture balances, compare the following:-
Heater
The air side energy output with the electrical input.
Humidifier
The air side total energy output with the electrical input, the moisture gained by the air with the measured heater usage to produce the steam.
Cooler coil
The moisture lost by the air with the rate of condensation.
Discuss the accuracy of the air conditions measurements to allow plotting the psychometric cycle and to obtain an energy and moisture balance on the heater, humidifier and cooler coil.
Marking scheme :
This laboratory report will carry 20% of the total module percentage.
This presentation will be marked:
• Literature Review 20%
• Technical content & Analysis Result 30%
• Conclusion 20%
• Referencing 10%
• Presentation of report (format & Graphics etc.) 20%
PREPARATION FOR THE ASSESSMENT
The reading list can be found in the link below:-
http://readinglists.central-lancashire.ac.uk/lists/B0CDB3A3-5382-3BEB-99DB-D992019B1E58.html
RELEASE DATES AND HAND IN DEADLINE
Assessment Release date: 8th November, 2022
Assessment Deadline Date and time: (21st Feb. 2023 11:59pm (HKT) for Class A)
(15th Feb. 2023 11:59pm (HKT) for Class B)
(23rd Feb. 2023 11:59pm (HKT) for Class C)
Please note that this is the final time you can submit – not the time to submit!
Your feedback/feed forward and mark for this assessment will be provided on 30th March, 2023
SUBMISSION DETAILS
The laboratory report (not more than 1250 words) will be submitted on the moodle of SHAPE complete with through Turnitin before assessment deadline.
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Version: 1
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Appendix A – Results and calculation
1. To calculate the air volume flow rate and the diameter orifice plate are required.
Record the following data:-
Air Flow Rate, m3/s
Diameter of Orifice, mm
2. Air Conditions
Plot the temperature against time and tabulate the following properties for each change of air condition.
Dry bulb temperature
Enthalpy
Wet bulb temperature (sling)
Moisture content
Dew-point temperature.
Specific volume
Plot the complete “air conditioning” cycle on a psychometric chart (for both conditions). (Note that to plot a cycle that “works” some air conditioning may have to be modified by calculations from the energy and mass balance).
Record the following data:-
2a. The first set of data (2 kW water heaters and 1 kW after-heaters):
t (make-up water), ºC
t (room air), ºC
tA (dry bulb), ºC
tA (wet bulb), ºC
wA, kg/kg
hA, kJ/kg
tB (dry bulb), ºC
tB (wet bulb), ºC
wB, kg/kg
hB, kJ/kg
tC (dry bulb), ºC
tC (wet bulb), ºC
wC, kg/kg
hC, kJ/kg
tD (dry bulb), ºC
tD (wet bulb), ºC
wD, kg/kg
hD, kJ/kg
Qb,s, kW
Qp, kW
Qa, kW
ma, kg/s
tcond (dry bulb), ºC
mcond, kg/s
h1, kJ/kg
h4, kJ/kg
mr, kg/s
Qb,l, kW
mw,b, kg/s
mw,a, kg/s
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2a. The first set of data (2 kW water heaters and 1 kW after-heaters):
%m, %
Q, kW
H, kW
%A-B, %
mw,c, kg/s
%cond, %
QB-C, kW
%B-C, %
QC-D, kW
%C-D, %
2b. The second set of data (2 kW water heaters, 2 kW pre-heaters and 1 kW after-heaters):
After 5 mins.
Dry bulb
Wet bulb
After 10 mins
Dry bulb
Wet bulb
tA (ºC )
tA (ºC )
tB (ºC )
tB (ºC )
tC (ºC )
tC (ºC )
tD (ºC )
tD (ºC )
After 15 mins.
Dry bulb
Wet bulb
After 20 mins
Dry bulb
Wet bulb
tA (ºC )
tA (ºC )
tB (ºC )
tB (ºC )
tC (ºC )
tC (ºC )
tD (ºC )
tD (ºC )
After 25 mins.
Dry bulb
Wet bulb
After 30 mins
Dry bulb
Wet bulb
tA (ºC )
tA (ºC )
tB (ºC )
tB (ºC )
tC (ºC )
tC (ºC )
tD (ºC )
tD (ºC )
After 35 mins.
Dry bulb
Wet bulb
After 40 mins
Dry bulb
Wet bulb
tA (ºC )
tA (ºC )
tB (ºC )
tB (ºC )
tC (ºC )
tC (ºC )
tD (ºC )
tD (ºC )
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2b. The second set of data (2 kW water heaters, 2 kW pre-heaters and 1 kW after-heaters):
After 45 mins.
Dry bulb
Wet bulb
After 50 mins
Dry bulb
Wet bulb
tA (ºC )
tA (ºC )
tB (ºC )
tB (ºC )
tC (ºC )
tC (ºC )
tD (ºC )
tD (ºC )
After 55 mins.
Dry bulb
Wet bulb
After 60 mins
Dry bulb
Wet bulb
tA (ºC )
tA (ºC )
tB (ºC )
tB (ºC )
tC (ºC )
tC (ºC )
tD (ºC )
tD (ºC )
6. Refrigeration
Record the following data:-
After 5 mins.
After 10 mins
Refrigerant Flow kg/s
Refrigerant Flow kg/s
After 15 mins.
After 20 mins
Refrigerant Flow kg/s
Refrigerant Flow kg/s
After 25 mins.
After 30 mins
Refrigerant Flow kg/s
Refrigerant Flow kg/s
After 35 mins.
After 40 mins
Refrigerant Flow kg/s
Refrigerant Flow kg/s
After 45 mins.
After 50 mins
Refrigerant Flow kg/s
Refrigerant Flow kg/s
After 55 mins.
After 60 mins
Refrigerant Flow kg/s
Refrigerant Flow kg/s
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7. Refrigeration (Cont’d)
Evaporator Pressure
Plow (kPa)
Condenser Pressure
Phigh (kPa)
Evaporator Temperature, t4
Evaporator Temperature, t1
Condenser, t2
TEV Inlet, t3
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Appendix B – Schematic , Laboratory Equipment and Relevant Charts
Fig. 1 Schematic Diagram of the Air-Conditioning Process
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Fig. 2 Photo of the Air-conditioning unit
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