This paper is s survey on an advanced attack for efficient air conditioning system utilizing evaporative chilling. The system uses merely H2O and dry air as fluids for air conditioning. The whole thought evolved during the air blushing activity of the grapevine in C2C3 Plant as portion of pre-commissioning activity.
Blushing of grapevine was carried out utilizing air with a dew point of -50 grades C. Means this is a really dry air. It was observed that, when dry air was passed through a grapevine holding some residuary H2O left, it caused chilling consequence, as a consequence, the out coming air was found to be really chilled. Besides there was some perspiration on the pipe line which means the H2O inside the grapevine is besides acquiring iciness.
From this phenomenon an thought was conceived that if a really dry air is passed through H2O with sufficient contact clip, it can be used for air conditioning consequence.
The air transporting wet with it will still be non really humid as ab initio it is really dry. The beauty of the procedure lies in the fact that merely at the cost of waterlessness both H2O every bit good as air is acquiring cooled. This can be efficaciously used in a closed H2O cringle and there would be no usage of any refrigerant.
2. Basic rule involved
Bulk air [ Temp, Hv ( Enthalpy ) ]
Hello
Water bead
Hi = Enthalpy of H2O bead
Interface.
Fig1: Micro degree heat transportation theoretical account of a H2O droplet
Modeling of procedure inside hair-raiser is being carried out where heat transportation accompanied by mass transportation takes topographic point.
There are three parallel heat transportation procedure traveling on here:
1 ) Latent heat transportation owing to vaporisation of H2O. This is the energy involved in stage alteration.
2 ) Reasonable heat transportation owing to temperature difference between air and H2O. This is the smallest portion of heat transportation.
3 ) Heat transportation accompanied by mass transportation ( diffusion ) of cold H2O to air. This becomes the major manner of heat transportation one time equilibrium is established.
Mentioning to the above fig 1,
As vaporisation occurs it causes a loss of energy in the H2O and that is being gained by air, the whole being a closed adiabatic system. This causes H2O to chill aggressively. Now see a state of affairs where mass transportation is high. This cool liquid zaping to air will transport cold energy along with it. This is what we have referred in ( 3 ) manner. The mass transportation of cold liquid from H2O watercourse to air watercourse is doing addition in humidness every bit good as chilling of air.
In this mold we assume the H2O droplet to be surrounded by a thin movie of air and heat content difference ( Hi – Hv ) between the movie and the environing provides the driving force for the chilling procedure. This H being a map of humidness ( ten ) every bit good as air temperature ( T ) gives a combined consequence of both manners of heat transportation.
3. PROCESS FLOW DIAGRAM
A little procedure flow diagram of the evaporative chilling is shown below.
Fig2: Block diagram of procedure
Air in ( 1 )
Water line
Chiller Air
38 deg C
RH=60 %
Ambient
Air Out ( 2 )
65 degC, 2.2kg/cm2
RH=60-80 %
Chilled ( 4 )
1.8kg/cm2 kg/cm2
RH= 45-60 %
T= 17-27 degC
( a )
1.8kg/cm2
Dry Air ( 3 )
T=50-55 degC
Dryer
RH=2-4 %
Dp= -7 to +5degC
1.9kg/cm2 22-26 degC
( B )
Make up Water ( vitamin E )
30degC ;
0.48-0.57m3/hr
Heat Exchanger
( degree Fahrenheit ) P=2.0kg/cm2
( 5 )
1.6 Kg/cm2 ( degree Celsius )
Suction P= 1.8kg/cm2
Water to be recycled
15-25 degC ;
RH=45-60 %
Air in to chiller
Air out from Chiller
Water circulation rate ( m3/hr )
Make up H2O
Reqd. ( m3/hr )
Air flow rate ( scfm )
T= 50-55degC
Dew point= -7 to +7degC
RH = 2-4 %
T=17-27degC
RH = 45-60 %
1.0
0.48-0.57
20,000
( C2-C3 control room )
Design footing: Equivalent to treat Control room HVAC system
Air blower is used which compresses the air to 2.2kg/cm2.This is basically a high volume low force per unit area centrifugal type blower. Above we have shown the operation for ambient temp 38degC and absolute humidness 60 % .When passed through the drier ( silica gel ) the humidness reduces to 2-4 % comparative humidness and temp ranges approx 50-55degC. Silical gel or any low cost drier is used because our waterlessness demand is less. Even a dry air with dew platinum -7 to +5 degC will be good plenty for this procedure. Next this dry air is passed through an adiabatic hair-raiser where H2O splashes over the dry air for interaction and H2O atoms diffuses into air thereby increasing its humidness. This hair-raiser is a normal spray tower with a high tantamount mass transportation interaction country. The figure of tantamount equilibrium phases is 3.The air coming out of hair-raiser is reasonably chilled and holding comparative humidness ( RH ) of 45-60 % ( For a normal HVAC system comfy zone of operation is between 45-60 % comparative humidness )
Humidity and temperature of the mercantile establishment can be controlled by mass flow rate of H2O. The beauty of the procedure is that both the H2O every bit good as air gets cooled due to loss of heat content of vaporisation and bulk motion of H2O droplets from H2O to air.
At the concluding phase of the procedure we have used a heat money changer so as to use the cold energy of chilled H2O coming out of hair-raiser. This ensures H2O to run in closed cringle for cold energy use.
4.Thermodynamic feasibleness
Chilling
Pressure
( Kg/cm2 )
Dryer recess
Blower recess
Temperature ( degC )
Fig 3: P-T curve for the whole procedure
For the above mentioned P-T diagram, thermodynamical survey for the information alteration was done for the adiabatic cooling portion.
Entropy alteration for the above mentioned procedure was derived as follows: a?†S ( alteration in information ) & A ; gt ; 0 and a?†H =0 ;
As there is a net addition in information, this proves that this procedure is thermodynamically executable procedure.
5.Specifications:
Footing: Air flow rate of 20,000 scfm.
Size of conditioning country = Process control room, C2C3 Plant Dahej
Specifications of the major equipements used for the above mentioned procedure:
1. Centrifugal type air blower:
Volume of air per min at fan mercantile establishment conditions = 20,000cfm.
Entire force per unit area = 2.2 kg/cm2.
Velocity force per unit area =0.1 kg/cm2.
Inactive pressure= 2.1kg/cm2.
2. Dryer design demands:
Drying from RH 70 % at 65 deg C to RH=2-4 % , 55degC
Pressure bead across it = 0.3 kg/cm2.
3. Hair-raisers: Spray type hair-raisers
No. of tantamount equilibrium stage= 3 ;
Pressure =1.8kg/cm2 ;
SIMULATION BLOCK ( utilizing ASPEN 11.1 )
Fig 4: Block agreement of simulation
As there is no standard air – H2O reaching hair-raiser form available in ASPEN, the simulation was carried utilizing a RADFRAC standard vas with nothing recondensor and reboiler responsibility. By trouble-shooting, optimal figure of equilibrium phase was found to be 3.
FOR INLET CONDITION-1 ( Normal operation )
Air in to chiller: Chiller pressure= 1.8 kg/cm2 ;
Dp = 0 degC ;
Temperature = 55degC
Temperature ( degC )
Relative humidness ( % )
Fig5: Variation of Air-out humidness with Air-out temperature
FOR INLET CONDITION-2
Air in to chiller: Chiller force per unit area = 1.8 kg/cm2 ;
Temperature= 55degC ;
Humidity ( Dp ) = +7 degC ; ( Not so dry air )
Fig6: Variation of Air-out humidness with Air-out temperature
Keeping hair-raiser P=1.8kg/cm2
Fig 7: Variation of Air-out temperature with Chiller force per unit area
For Air-in [ Humidity ( Dp = 7 degC ) ; Temp=55degC ]
Fig 8: Variation of Relative humidness ( % ) of Air-out vs Chiller force per unit area ( kg/cm2 )
for Air-In [ humidness ( DP = +7degC ) ; Temp=55degC ]
Fig9: Coincident dependance of
Chiller Pressure ( kg/cm2 ) – Air out RH ( Dp ) – Air out Temp ( degC )
[ For Air recess to chiller: Dp= +7degC ; Temp =55 degC. ]Appendix: Snapshots of Simulation inputs and consequences
