8th International Conference on Soft Computing, Mathematics and Control (SMC ...
Rac 180523050147
1. VARIATION SHF FOR AIR CONDITIONING IN
SUMMER AND WINTER CONDITIONS
PRESENTED BY:
11BME007 - KUSH BHANVADIYA
15BME014 - KRISHNA BHUVA
13BME040 - KULDEEEP JADEJA
11BME045 - CHARCHIT JOSHI
11BME055 - CHANDNI BHUVA
2. INTRODUCTION
Air conditioning is a process of removal of heat or humidity to improve the
comfort of occupant.
This process is most commonly used to achieve a more comfortable
interior environment, typically for humans or animals; however, air
conditioning is also used to cool/dehumidify rooms
Psychrometry is the study of physical and thermodynamic property of
miture of gas-vapour. It has many applications in heating, cooling,
ventilating, and air-conditioning.
3. psychometric properties:-
Dry-bulb temperature (DBT):-
It it’s the temperature of air as measured by a thermometer.
Wet-bulb temperature (WBT):-
The thermodynamic wet-bulb temperature is a thermodynamic property of
mixture of air and water vapor. The value indicated by a wet-bulb thermometer
often provides an adequate approximation of the thermodynamic wet-bulb
temperature.
A psychometer is a device that includes both a dry-bulb and a wet-bulb
thermometer.
Dew point temperature:-
It can also be defined as the temperature at which the vapour changes into
(condensation). Usually the level at which water vapor changes into liquid marks
the base of the cloud in the atmosphere hence called condensation level. So the
temperature value that allows this process (condensation) to take place is called
the 'dew point temperature'.
4. Relative humidity: - It is defined as mole fraction of moist air in saturated
pressure at same temperature and pressure.
Specific humidity: - It is defined as the proportion of the mass of water
vapour and mass of the moist air sample.
Degree of saturation : The degree of saturation is the ratio of the
humidity ratio W to the humidity ratio of a saturated mixture Ws at the
same temperature and pressure.
Enthalpy: The enthalpy of moist air is the sum of the enthalpy of the dry
air and the enthalpy of the water vapour. Enthalpy values are always
on some reference value. For moist air, the enthalpy of dry air is given a
zero value at 0oC, and for water vapour the enthalpy of saturated water is
taken as zero at 0oC.
5. All this properties can be calculated with the help of a psychometry chart. It is
important for us to have a proper idea of how to study psychometric chart so that
we can calculated the process needed to get in the area of comfort zone.
Psychometric charts are available at standard barometric pressure of 101.325 kPa at
sea level and for normal temperatures (0-50oC).
Lines of constant dry bulb temperature run vertically up the psychrometric chart.
The dry bulb temperature is what if measured by a normal air thermometer.
6. The vertical axis represents the water vapor in the air and is commonly referred to
as the Humidity Ratio. A horizontal line represents a constant amount of water
vapor in the air. It no water is added to the air, humidification, or removed from
the air, dehumidification, then any change in air properties will follow this line.
The chart becomes more complex as more lines are added. Another essential line
is constant relative humidity. The primary use of the constant relative humidity
line is to identify a point on the chart. A simple example is that if you raise the air
temperature and do not add water vapor, constant humidity ratio, the relative
humidity decreases. So while the humidity is lower in the hottest part of the day,
the moisture in the air has not changed.
7.
8. Importance of SHF factor
Total heat is comprised of sensible heat and latent heat. SHF (SENSIBLE
HEAT FACTOR) is the ratio between the sensible and the total heat.
The factor comes handy for the ‘building specifications’ point of view. The
factor is greatly influenced by the relative humidity and the working
conditions of the air coolers.
By SHF the latent and sensible cooling or heating loads on a building can
be estimated. It’s the basic ratio and yet the a very important one
whenever cooling load is estimated for a room.
9. SHF
The heat added during psychometric process may be split into sensible heat and latent heat. The ratio
of sensible heat to total heat is called sensible heat factor,
SHF=SHSH+LH
Where, SH = sensible heat and LH = latent heat.
10. Different possible processes:
1. Process 1-2A : Heating & Humidification[ ts > t1] , where ts is the mean surface
temperature of water droplets. Mean surface temperature (ts) greater than the dry bulb
temperature. Here water is externally heated.
2. Process 1-2B : Humidification [ts =t1] Enthalpy of air increases. Water is required to be
externally heated.
3. Process 1-2C: Cooling & Humidification[ t1 < ts < t1] where is t1 wet temperature. Air is
cooled, enthalpy increases as a result of humidification. Water is required to be externally
heated.
4. Process 1-2D Adiabatic saturation [ t1 = ts ] where is t1 wet temperature .Pumped
circulation of water. Without any external heating or cooling.
5. Process 1-2E : Cooling & Humidification[ td < ts < t1 1] Similar to 1-2C with difference
that the enthalpy of air decreases. Water is required to be externally cooled.
6. Process 1-2F : Cooling [ts = td] where td is the dew point temperature. . Water is required
to be externally cooled.
7. Process 1-2G: Cooling & Dehumidification[ts < td ] air is simultaneously cooled and
dehumidified.
11. OBJECTIVE
In this project effect of summer and winter conditions on air conditioning
was studied. Specifically, the effect of SHF factor was calculated during
summer and winter. The results were seen to have considerable variability
for different temperature inputs, but it was also seen that there was a
strong positive. Later on, possible causes for this variation were looked
into and observations were made.
12. METHODOLOGY
The accessibility of video technology has made it possible to utilize both
the auditory and visual channels to present the project. We started our
project by watching videos and reading the research papers. So for the
further analysis we required more depth of the topic. We studied R.S
Khurmi book and finally we started our work. Firstly we distributed topic
for everyone. The main aim of our project was to do the analysis on the
SHF factor. We studied that the factor is greatly influenced by the relative
humidity and the working conditions of the air cooler. For calculating SHF
factor firstly we made a code that would determine the SHF factor
whenever the values of dry bulb temperature and wet bulb temperature of
inside and outside of the room is given as input. We required something
to be fixed for the conclusion so we fixed the room temperature to our
comfort zone. Now, since the temperature inside the room is fixed,
variation of SHF based on different seasons can be found out by analysis.
13. Hand calculation
Specific Humidity :-
𝜔 = 𝑚 𝑣/𝑚 𝑎
= V*𝑣 𝑎/V*𝑣𝑣 = 𝑣 𝑎/𝑣 𝑣
Substituting for mv and ma from these equation in above equation, we obtain
𝜔 = Mvpv / Mapa = 18.016pv/28.966pa = .600pv/pa
𝜔 = .662pv/p-pv
18. MATLAB
MATLAB code :-
clc;
clear all;
T1=input('enter the value of dry bulb temperature inside the room:');
T_1=input('enter the value of wet bulb temperature inside the room:');
T2=input('enter the value of dry bulb temperature of the atmosphere:');
T_2=input('enter the value of wet bulb temperature of the atmosphere:');
y=input('enter barometric pressure in N/m^2:');
%barometric pressure is near to 101325 normally
x=zeros(4,1);
display('the pressure values for DBT and WBT at inside and outside the room are
as follows');
19. %saturation pressure @DBT in the room=ps
XSteam('psat_T',T1)
x(1,1)=ans;
%saturation pressure @WBT in the room
XSteam('psat_T',T_1)
x(2,1)=ans;
%saturation pressure @DBT outside the room=p
XSteam('psat_T',T2)
x(3,1)=ans;
%saturation pressure @WBT outside the room
XSteam('psat_T',T_2)
x(4,1)=ans;
%convert into N/m^2
x=x*100000;
%pv1 value
pv1=x(2,1)-(y-x(2,1))*(T1-T_1)*(1.8)/(2800-1.3*(1.8*T1+32));
pv2=x(4,1)-(y-x(4,1))*(T2-T_2)*(1.8)/(2800-1.3*(1.8*T2+32));
21. Output :-
enter the value of dry bulb temperature inside the room:22
enter the value of wet bulb temperature inside the room:14
enter the value of dry bulb temperature of the atmosphere:15
enter the value of wet bulb temperature of the atmosphere:6
enter barometric pressure in N/m^2:101325
the pressure values for DBT and WBT at inside and outside the room are as follows
ans =0.0265
ans =0.0160
ans =0.0738
ans =0.0140
RH1 = 0.4039
RH2 = 0.1983
W1 = 0.0066
W2 = -0.0021
h1 = 39.3210
h2 = 20.589
SHF = 0.3812
23. Result and conclusion
Based on the result we need to find value of SHF. Generally, we get different
values based on different conditions for different seasons for summer season
we get nearly 0.7 and for winter season we get value of 0.3 ideally. When
different values of DBT and WBT are inserted different results are obtained.
Results show that for temperature above comfort zone i.e, for 40oC DBT and
higher WBT 29oC and 25oC we are getting result of 0.33 and 0.55 respectively.
And at lower DBT of 8oC and WBT 3oC and 6oC we are getting value of 0.58 and
0.76 and at 15oC and 6oC we are getting 0.38.
We are getting a significant amount of error it can be justified due to bypass
factor of the AC. It can be due to by-pass factor larger will be the difference
between air outlet temperature and the cooling coil temperature. When BPF is
1.0, all the air by-passes the coil and there will not be any cooling or de-
humidification.
24. Nowadays all year AC systems are also there which can work for all the
purposes of humidifying, cooling in summer for getting desired values.
The humidification is obtained by operating the cooling coil at lower
temp. than the dew point. In winter, the cooling coil is made inoperative
and the heating coil operates to heat the air. The spray type humidifier is
also used to humidify the air.
25. references
Refrigeration and Air Conditioning by C.P.Arora
Refrigeration and Air Conditioning by R.S. Khurmi
Engineeringtoolbox.com
nptel.ac.in
mesubjects.net
