This document describes an experiment analyzing the properties of moist air using an air conditioning laboratory unit. Measurements of dry and wet bulb temperature were taken at different sections of the unit as air passed through a humidifying and preheating section and reheating section. The experimental results demonstrated how air conditioning processes can condition air to desired levels of temperature and humidity for occupant comfort regardless of external conditions. Calculations using psychrometric charts and equations were performed to determine air properties at each section.

1. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 1 | P a g e
refrigeration &air-conditioning
Laboratory
University of Baghdad
Name: - Saif Al-din Ali

2. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 2 | P a g e
TABLE OF CONTENTS
ABSTRACT.........................................................................I
INTRODUCTION..............................................................II
APPARATUS...................................................................III
Calculations and results...................................................V
DISCUSSION .................................................................VI

3. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 3 | P a g e
Experiment Name:- Moist Air Properties and Air-Conditioning Processes
1. Abstract
An air conditioning process which consists of maintaining a living space or
facilities at a desired temperature and humidity was analyzed using an Air
Conditioning Laboratory unit. This experiment demonstrates how an air
condition works and the application of psychrometric chart to read the
properties of air for each section on an air conditioning unit, which consists
of untreated air entering the ducting and going through a humidifying and
preheating section and a reheating section. Measurements of dry and wet
bulb temperature were taken at each section of the process. The
experimental results indicated that air can be conditioned to desired levels
to maintain the health and comfort of the occupants or to meet the
requirements of industrial process irrespective of the external climatic
conditions.
2. Introduction
Air conditioning is the conditioning of air within a defined space, usually a
residence or a place of business. Conditioning usually involves heating
or cooling, humidifying or dehumidifying, and filtering or cleaning air and
controlling its moisture level: conditioning it to provide maximum indoor
Comfort, An air conditioner transfers heat from the inside of a building,
where it is not wanted, to the outside. Refrigerant in the system absorb
the excess heat and is pumped through a closed system of piping to an
outside Coil. A fan blows outside air Over the hot coil, transferring heat
from the refrigerant to the Outdoor air. It is because the heat is removed
from the indoor air, the indoor area is Cooled,
Air - conditioning is a system giving automatic Control of the required
environmental conditions, by method of heating, cooling, humidification,
deliumiclification), cleaning and movement of air in the building, vehicles
and others.
These control conditions may be desirable to maintain the health and
comfort of the occupants or to meet the requirements of industrial
process irrespective of the external climatic conditions.

4. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 4 | P a g e
3. APPARATUS
Th apparatus used for this experiment has the following components
1. A centrifugal fan with spend control
2. Pre-hater
3. Steam injector / humidifier
4. Re - heater:
5. Wet and dry bulb manometer.
6. pressure gauges
7. Condenser:
8. Evaporator
The following diagram in fig, shows an air conditioning unit used for
this experiment,

5. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 5 | P a g e
4. Calculations and results
Use MATLAB for equations
Pv=vapor pressure in KPa
Pb= barometric pressure in KPa (101.325)
Pv=Psw-Pb*A*(Td-Tw)) A=6.6*10^-4 Tw >=0 or A=5.94*10^-4 Tw <0
RH=(Pv/Ps)
W=0.622*(Pv/Pb-Pv)
h=(1.007Td-0.026)+W(2501+1.84Td)
Linear interpolation calculator for ps&pws
Tc` P (KPa) Tc` P (KPa)
18.4 2.11774 18.9 2.1845
18.6 2.1446 19 2.1979
13.9 1.5886 13 1.4979
14 1.5987 12.2 1.349
7.1 1.00909 9 1.1481
9.2 1.164 21.8 2.6134
24 2.9852 30.6 4.3961
10 1.2280
clc
clear
Td=input('entre Td ; ');
Tw=input('entre Tw ; ');
Psw =input('entre psw at Tw ; ' );
ps=input('entre ps at Tb ; ' );
pv= Psw-0.0675*(Td-Tw)
R=pv/ps
w=0.622*(pv/(101.325-pv))
h=(1.007*Td-0.026)+w*(2501+1.84*Td)

6. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 6 | P a g e
The solution to equations
HEATING
NO Td c` Tw c` Pv Kpa RH %
W
kg/kg
h kj/kg
1 18.4 12.2 0.9305 43.95 0.0058 33.462
digital 2 18.6 13.9 1.2713 59.29 0.0079 38.7415
3 24 19 1.8604 62.32 0.0116 53.7523
digital 4 30.6 21.8 2.0194 45.94 0.0126 63.134
COOLING
5 19 13 1.0929 49.72 0.0068 36.3061
digital 6 18.9 14 1.268 58.04 0.0079 38.9937
7 10 9 1.0806 88 0.0067 26.93
digital 8 9.2 7.1 0.8673 74.51 0.0054 22.7604

7. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 7 | P a g e
5. DISCUSSION
1. Explain the benefits of psychrometric chart in solving air condition
problems
The process of analyzing the air entering through the temperatures to
reach the levels required to maintain human comfort, regardless of
external conditions
psychrometric
heating
NO Td c` Tw c`
v
m^3/kg
RH %
W
kg/kg
h kj/kg
T dew
c`
1 18.4 12.2 0.835 48 0.0063 34.5 7.2
digital 2 18.6 13.9 0.838 59 0.0079 39.5 11.7
3 24 19 0.858 62 0.00117 54.5 16.4
digital 4 30.6 21.8 0.878 47 0.00128 63.5 17.8
cooling
5 19 13 0.838 50 0.0068 37 8.5
digital 6 18.9 14 0.838 59 0.0079 38.5 10.6
7 10 9 0.812 80.8 0.0066 27.5 8
digital 8 9.2 7.1 0.0808 75 0.0055 23 4.5

8. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 8 | P a g e
2. Specify the state at which the dry bulb and wet bulb temperatures are
equal
When the air humidity reaches saturation level, there will be
no heat loss or gain
3. When calculating the properties of moist air, dry air and water vapor
are treated separately, explain why?
Moist air is a two-phase (binary) mixture of dry air (i.e., atmospheric air with all
water vapor and contaminants removed) and water vapor that needs to be treated
separately from dry air since its physical properties are different. The homogeneous
mixture of dry air and water vapor that do not react with each other and do not
change in chemical composition is considered a pure substance. Moreover, because
none of the components of dry air is highly soluble in liquid water, dry air
composition can be considered invariable, even if small variations in the amounts of
individual components occur with time, geographic location, and altitude
(McQuiston and Parker 1988).
4. Discuss the air conditioning processes that are performed in the experiment and the
results obtained.
Cooling is the transfer of energy from the space or air supplied to
the space by virtue of a difference in temperature between the
source and the space or air. In the usual cooling process air is
circulated over a surface at a low temperature. Cooling usually
denotes sensible heat transfer, with a decrease in the air
temperature.
Heating is the transfer of energy to a space or to the air in a space
by virtue of a difference in temperature between the source and
the space or air. Heating can take place through direct radiation
and free convection, heating of forced circulated air, heating of
water that is circulated to the vicinity space.
Dehumidifying is the transfer of water vapor from the
atmospheric air. Latent heat transfer is associated with this

9. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 9 | P a g e
process. This process is most often accompanied by circulating
the air over a surface maintained at a sufficiently low temperature
to cause the condensation of water vapor from the mixture.
Humidifying is the transfer of water vapor to atmospheric air. This
process is usually accomplished by introducing water vapor or
by spraying fine droplets of water that evaporate into the
circulating air stream.
The reason for the difference in readings is due to the
accuracy of the device, the user’s experience, the way to deal
with the devices, the device’s age, and the calibration process
for the measuring devices

10. Saif al-din ali Madi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/1/2020 10 | P a g e
5. What factors are considered in measuring the wet bulb temperature and what is the
recommended air speed over the wet bulb in a Sling Psychrometer?
The wet bulb temperature Tw (or tw) or isobaric wet bulb temperature, is the
temperature an air parcel would have if adiabatically cooled to saturation at
constant pressure by evaporation of water into it, all latent heat being supplied by
the parcel. This temperature is directly measured by the wet bulb of a psychrometer,
or can be obtained indirectly by means of a psychrometric diagram or formula, after
the dry bulb temperature and any one hygrometric value (i.e. e, MR, SH, AH, RH or
DP) are known. From the thermodynamic point of view, Tw is the temperature that
an air parcel would have when some liquid water is supplied gradually, in very small
quantities and at the same temperature as the environmental air, and then this
water is evaporated into the air adiabatically (i.e. the latent heat being supplied by
the air) at constant pressure, until saturation is reached. Saturation is reached for
the combined action of two factors due to the evaporation: the increase in MR and
the drop in T. Consequently, Tw is the lowest temperature that an air parcel would
have by evaporating water, the latent heat being subtracted from the air and utilized
for the change of state of water from liquid to vapour, until saturation is reached. Tw
is also the equilibrium temperature of an evaporating surface of water.
Applying the first law of the thermodynamics to an air parcel formed of 1 g of dry air
with a mass of vapour mv, i.e. with mixing ratio w = mυ, and experiencing the above
process,
Humidity rate
Atmospheric pressure
The accuracy of the device used
Air velocity
Engineering sense when measuring