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Mechanical Engineering Department
ME322 Thermo fluids Laboratory
Air Conditioning
“Long Report”
Prepared by
مكئاعالتنسوني من صالح د حالالتنسوني من ص نالتنسوني م ينوسنتال
436xxxxxx
Class:
Group:
Supervised by
Dr. Jamel A. Orfi
1 st of April 2019
25/7/1440H
Abstract
In this experiment, the air conditioning system has been experienced at three
different configurations. First, with the pure sensible cooling process using
the vapor- compression system, then with the pure sensible heating process
using electric heaters system, and lastly with the pure humidification of air
process using steam injection. The purpose of these three configurations is to
obtain a clear observation of each process’s parameters.
List of figures and tables
FIGURES:
Figure 1 Air conditioning and refrigerating devices..................................................................................... 5 Figure 2 Air conditioning laboratory unit A660 with upgrades A661A, A660C, A660D and AC661A........... 8 Figure 3 Psychometric chart for the sensible cooling process................................................................... 12 Figure 4 Psychometric chart for the sensible heating process.................................................................. 13 Figure 5 Psychometric chart for the sensible humidification process....................................................... 13
TABLES:
Table 1 the data obtained from the experimental apparatus................................................................... 10 Table 2 Thermodynamics properties obtained from EES.......................................................................... 11 Table 3 Results and error calculations for cooling process....................................................................... 11 Table 4 Results and error calculations for heating process....................................................................... 11 Table 5 Results and error calculations for humidification process............................................................ 12 Nomenclature
P Pressure (kPa)
T Temperature (℃)
HEnthalpy (kJ)
ωSpecific humidity (kg of water vapor/kg of dry air)
∅ Relative humidity
COP Coefficient of performance
Z Orifice head (cm)
m ̇ Mass flow rate (kg/sec)
Q ̇ Heat (kW)
Introduction
One of the most useful thermodynamics principles is air conditioning
applications. The second law of thermodynamics is applied, which is
concerned with the dedicated devices of removing heat from a certain space.
Air conditioning has become the lifeblood in many countries and applications,
starting with medical and ending with entertainment.
Figure 1 Air conditioning and refrigerating devices
Refrigeration and air conditioners have three capabilities, whether to cool,
heat, humidify, and dehumidify. Cooling is known by rejecting heat of the
space, and heating is adding heat to that space from an external system.
However, humidification is the process of extracting water stream and inject
into the system by the help of a boiler, whereas dehumidification is the
reversed process.
All these processes are important at varied conditions. For instance, the
cooling process is needed at summer season to avoid hot weather, while
during winter nights the heater is essential to keep the temperature warm. In
addition, in case of low relative humidity, the use of humidification will raise
the humidity in the space, and the vice versa for the dehumidification process.
These devices in (figure 1) were created for human comfort in buildings.
Theory
There are three processes that needed to be analyzed, cooling, heating, and
humidification. Each process has its own equations.
The specific volume can be calculated using the following equation:
For the mass flow rate of the air:
9 ̇ = 0.0517 × √ Where:
z: the differential head of the orifice meter
v: the specific volume of the air
The heat rate for the preheated coils:
̇ = 2
The heat rate for the cooling refrigerant:̇
=̇ (ℎ −ℎ )
.. 1 4 The first law of thermodynamics which is used for the heater: ̇ ℎ + + =̇ ℎ ̇
The mass flow rate of the moisture, which is used for humidifying:
̇ =̇ ( − )
Methodology methodology Figure 2 Air conditioning laboratory unit A660 with upgrades A661A, A660C, A660D and AC661A
Results
Table 1 the data obtained from the experimental apparatus
Wet t10 °C 17.
Duct Differential Pressure Ze mm 9.
A'' Air at Fan inlet Dry t1 °C 19.
injection Wet t4 °C 14.
E'' Return Air Dry t9 °C 21.
Steam Enthalpy =hg P1 kj/kg 2672.
- List of figures and tables.....................................................................................................................................
- Figures....................................................................................................................................................................
- Tables......................................................................................................................................................................
- Nomenclature..........................................................................................................................................................
- Introduction.............................................................................................................................................................
- Objectives..................................................................................................................................................................
- Theory.........................................................................................................................................................................
- Methodology.............................................................................................................................................................
- Experiment Setup..............................................................................................................................................
- Procedure..............................................................................................................................................................
- Results......................................................................................................................................................................
- Sample of calculation.....................................................................................................................................
- Discussion...............................................................................................................................................................
- Recommendation.................................................................................................................................................
- Conclusion..............................................................................................................................................................
- References.............................................................................................................................................................. - B Before cooling Dry t3 °C 15. Test Units Values - Wet t4 °C - Cooling C After cooling Dry t5 °C 10. - Wet t6 °C 10. - E Return Air Dry t9 °C 12. - Wet t10 °C 12. - A' Air at Fan inlet Dry t1 °C 20. - Wet t2 °C 10.
- Heating B' After pre-heat or steam injection Dry t3 °C 28. - Wet t4 °C 13. - E' Return Air Dry t9 °C 27. - Wet t10 °C 17. - Evaporator Outlet t13 °C - Condenser Outlet t15 °C - Supply Volts V L V - Evaporator Outlet pressure P1 kPa - Condenser Inlet pressure P2 kPa - Condenser Outlet pressure P3 kPa - Duct Differential Pressure Ze mm 9. - Fan Supply Voltage Vf V - Fan Power Pf kW 0. - Heater Resistance Rp Ω 45. - R132a Mass Flow Rate mref kg/s 0. - A'' Air at Fan inlet Dry t1 °C 19. - Wet t2 °C 11.
- Humidification B'' After pre-heat or steam Dry t3 °C 20. - injection Wet t4 °C 14. - E'' Return Air Dry t9 °C 21. - Wet t10 °C 18. - Duct Differential Pressure t13 mm 7. - Fan Supply Voltage t15 V - Fan Power V L kW 0. - Steam Enthalpy =hg P1 kj/kg 2672.
Table 2 Thermodynamics properties obtained from EES
Cooling hB [kJ/kg] 43. hC [kJ/kg] 32. wB [kg/kg] 0. wC [kg/kg] 0. h1 ref. [kJ/kg] 254 h4 ref. [kJ/kg] 105 Heating hA [kJ/kg] 31. hB [kJ/kg] 39. [kg/kg] 0. [kg/kg] 0. Humidification hA [kJ/kg] 33. hB [kJ/kg] 43. [kg/kg] 0. [kg/kg]^ 0. hst [kJ/kg] 2672.
Table 3 Results and error calculations for cooling process
Sensible Cooling Process Quantity Theoretical Graphical Error, % Specific volume [m^3/kg] 0.863265789 0.888 2. Mass Flow Rate, ma [kg/s] 0.17330 0.17087 1. Q cooling, Qc [kW] 2.0398 2.0112 1. Q cooling for Ref, Qref [kW] 1.8625 8.
Table 4 Results and error calculations for heating process
Sensible Heating Process Quantity Theoretical Graphical Error, % Specific volume [m^3/kg] 0.908279474 0.894 1. Mass Flow Rate, ma [kg/s] 0.14657 0.14773 0. Heat from coil, Qp [kW] 1.0637 - Enthalpy at B, hB [kJ/kg] 40.09638976 39.52 1.
Figure 4 Psychometric chart for the sensible heating process Figure 5 Psychometric chart for the sensible humidification process
SAMPLE OF CALCULATION:
- For cooling: 9 0.287 × (15.7 + 273.15) 3 = = 95 9.7 = 0.8633/
̇ = 0.0517 × √ = 0.0517 ×
̇^ =̇^ (ℎ^ − ℎ^ ) = 0.1733 × (43.81 − 32.04) = 2. =̇ (ℎ − ℎ ) 4 = 0.0125 × (254 − 105) = 1. ̇.. 1 | ℎ − ℎ | % (^) ̇ = (^) | ℎ | × 100 |2.0398 − 1.8625| = |2.0398| × 100 = 8.69 %
- For heating ̇^2 = (^) = 45.5 × 1000 = 1. ̇ ℎ + + 0.14657^ × 31.61 + 0.19 + 1.
̇
̇
- For humidification: ̇ =̇ ( − ) = 0.148 × (0.0043 − 0.004374) = 0.0005 / ℎ = ̇ℎ ++̇ ℎ ̇
= 0.148 × 33.37 + 0.19 + 0.0005 × 2672.7 = 43.1 /
Discussion
It can be seen from (figure 4) that the temperature in the heating process will
increase. However, the slope is a little bit shelved which indicates an
occurrence of dehumidification, which is totally unexpected and it’s so small
to be considered. Comparing it with (figure 3), the slope of the cooling process
is more acute than the slope at the heating process. In addition, the slope
draws the humidification relationship to cooling. Looking at (figure 5), it
shows that the humidification process has only slight effects on the
temperature. The reason behind the increase of the temperature is the
injected steam temperature.
With regards to the calculated errors shown in table (1), (2), and (3), it can be
noticed that all of them are in the safe region, and the causes of these errors
can be assigned to the mistakes in observation of the readings, losses of heat
at the duct as it can be sensed when touching it, calibration errors, vibration in
the experiment apparatus which obviously has affected the efficiency, and the
human errors in using the psychometric chart.
In the following section (recommendations), I’ll write about the ways to
enhance the results.
Recommendation
1- To get more accurate results, more readings must be taken.
2- To get a more uniform flow, a more stable fan must be installed
3- To minimize the amount of heat loss, perfect insulation must be used for
both the condenser and the evaporator.
4- Using more advanced calculation software.
Conclusion
To conclude, the experiment was aimed to study three common processes in
air conditioning, calling, heating, and humidification. There are many
variables that have been measured and calculated in our experiment, such as,
the specific humidity, enthalpy, specific volume, mass flow rate, and heat
energy. Most of them were found by the help of a psychometric chart and the
thermodynamic principles.
The margin of the errors in the experiment is acceptable since the highest error
is 8.69% in ̇.
However, the errors in our experiment have mainly occurred due to the heat
losses in the apparatus and the calibration errors.
