Condenser & Evaporator

21
8/22/2019 Condenser & Evaporator http://slidepdf.com/reader/full/condenser-evaporator 1/21  Design o f Air coo led evapo rator manually Air cooling evaporators for cold rooms, blast freezers, air-conditioning, etc., will have finned pipe coils in all but very small coolers, there will be fans to blow the air over the coil. Construction materials will be the same as for air-cooled condensers. Aluminum fins on copper tube are the most common for the halocarbons, with stainless steel or aluminum tube for ammonia. Frost or condensed water will form on the fin surface and must be drained away. To permit this, fins will be vertical and the air flow horizontal, with a drain tray provided under. The size of the tube will be such that the velocity of the boiling fluid within it will cause turbulence to promote heat transfer. Tube diameters will vary from 9 mm to 32 mm, according to the size of coil. Fin spacing will be a compromise between compactness (and cost) and the tendency for the spaces to block with condensed moisture or frost. Spacings will vary from 2 mm on a compact air-conditioner to 12 mm on a low-temperature cold-room coil. We will design manually and by Techinsolve software

Transcript of Condenser & Evaporator

Page 1: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 1/21

 

Design o f Air coo led evapo rator manual ly 

Air cooling evaporators for cold rooms, blast freezers, air-conditioning, etc., will have

finned pipe coils in all but very small coolers, there will be fans to blow the air over the

coil. Construction materials will be the same as for air-cooled condensers. Aluminumfins on copper tube are the most common for the halocarbons, with stainless steel or 

aluminum tube for ammonia. Frost or condensed water will form on the fin surface and

must be drained away. To permit this, fins will be vertical and the air flow horizontal,

with a drain tray provided under. The size of the tube will be such that the velocity of 

the boiling fluid within it will cause turbulence to promote heat transfer. Tube

diameters will vary from 9 mm to 32 mm, according to the size of coil. Fin spacing

will be a compromise between compactness (and cost) and the tendency for the spaces

to block with condensed moisture or frost. Spacings will vary from 2 mm on a compact

air-conditioner to 12 mm on a low-temperature cold-room coil.

We will design manually and by Techinsolve software

Page 2: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 2/21

 

Evaporator Design : 

From the psychrometric chart:

Inlet condition:

dbta in=380c & wbta in=33

0cha in=114.15kj/kg & Wa 1=0.01585 kgw/kga

TDP=21.20c

Outlet condition:

C.S.H.F=0.40 & RH=100%ha out=90 kj/kg

 Cooling load:

Qc =a ha in ha out)

123 =a (114.15 90) a=

5.02kg/sec.

Coil design:

:side (ref.)TubeFor

 

 

( )  

( )    

:For air side

 

 

* + ( ) 

( ) 

 

 

Page 3: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 3/21

 

   

 

 

R=0.75 kj/kg.k 

Ts1 √ 

√   

Ts1 =30.56

0

c

Ts1 ˃TDP wet surface

Ts2 √ 

√   

Ts2 =25.450

c

∆Trm=

 

=

 = 20.9 0c

Ai=   

=

= 3 m2 

Ao=Ai*(18.5)= m2 

 Nr=6

ref =  

0.898=

 

 Nc 26

Page 4: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 4/21

 

 NC= 

H =26*0.0254 = 0.66 m

Aface= 

=1.731 m2 

Aface=H*LL = 2.62 m

Tube length:

L =

  Nt = 24 tubes 

Fin calculations

Assume

 

⁄  

   

 

(

)

 

( ) 

 

 From chart

  

   

Assume w=15cm

   

 

 

 

Page 5: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 5/21

    

 

 

  )

 

   

 

 

 

 

 

Page 6: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 6/21

 

Techn isolv e Software for Evaporator coi l design 

Manufactur ing design proc edure: 

1st Step:

Page 7: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 7/21

 

2nd Step:

Page 8: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 8/21

 

3rd Step (Run Calculation from F9 button or button):

Coil Manufacturing Report

Recoil (5/8 inch - 38.1x50.8)

1016 x 1264 4r 6f 40c

DX 15938 / 20 / 04 / 6.00 / 1264 Cu/GI (40)

Areas and VolumesAo = 86.919 m²

Ao' = 16.921 m²/face m²-rows

Ai = 5.389 m²

Vi = 20.9 Litre

Pipe ConnectionsSize = 67 mm

Heat Transferho = 44.102 W/m²°C

Ui = 3.780 kW/m²°CUo = 36.800 W/m²°C

 Ntu = 0.434

Cr = 0.000

Qt = e x Qmax

= 0.352 x 350.216 = 123.242 kW

Air Side DutyQt = ma (hao - hai)

= 3.504 (87.49 - 122.66) = -123.242 kW

Qs = ma x Cpa (dbo - dbi)

= 3.504 x 1.066 (28.3 - 38.0) = -36.308 kWRate = 39.156 kW/cms

Psychrometrics

Bypass factor = 0.358

Apparatus Dew Point = 22.8 °C

Refrigerant (R134a) DutySuperheat = 7.5 °C

Mass flow = 0.790 kg/s (approx)

Mass flux = 101.7 kg/sqm.s (approx)

Velocity = 0.080 m/s

Qt = mr x dh= 0.790 x 156 = 123.26 kW

Dimensions

Height 1016.0 mm

Length 1264.0 mm

Depth 152.4 mm

Rows 4

Fins 6.00 fpi

Weight 135.4 kg

Page 9: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 9/21

 

CircuitingTubes High 20

Tube Count 80

Circuits 40

Circuit Basis Tubes high

Tubes/Circuits 2

Unlinked tubes 0

Serpentine 2

Eq Length 3.8 mConnections Same end

Tube (Staggered Pattern)ID 15.723 mm

OD 16.586 mm

Sx 38.100 mm

Sy 50.800 mm

FinThickness 0.200 mm

Area factor 1.000 mm

MaterialFin Cu

Tube Cu

Casing GI

Page 10: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 10/21

 

Psychrometric Chart :

Page 11: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 11/21

 

Condenser

Condenser is an important component of any air conditioning system. In a typical

refrigerant condenser, the refrigerant enters the condenser in a superheated state. It is

first de-superheated and then condensed by rejecting heat to an external medium. The

refrigerant may leave the condenser as a saturated or a sub-cooled liquid, depending

upon the temperature of the external medium and design of the condenser.

 Classif icat ion of con densers (Based on th e external f luid) : Air cooled condensers (will be used in our case study so we will concentrate on it).

Water cooled condensers (discussed before in chapter 2).

Evaporative condensers (discussed before in chapter 2).

Air cooled condensers:

The circulation of air over the condenser surface is maintained by using a fan or a

 blower. These condensers normally use fins on air-side for good heat transfer. The fins

can be either plate type or annular type. This type of condensers is commonly used in

window air conditioners, water coolers and packaged air conditioning plants. The face

velocity is usually around 2m/s to 3.5 m/s to limit the pressure drop due to frictional

resistance. The coils of the tube in the flow direction are called rows. A condenser may

have two to eight rows of the tubes carrying the refrigerant. The moist air flows over 

the fins while the refrigerant flows inside the tubes. The fins are usually of aluminum

and tubes are made of copper. 

Holes of diameter slightly less than the tube diameter are punched in the plates and

 plates are slid over the tube bank. Then the copper tubes are pressurized which expands

the tubes and makes a good thermal contact between the tube and fins.

Air Cooled Condenser design :We will design the Air cooled condenser by Software and manually

To design the Air cooled condenser by Software, we will use ( Technisolve air cooled

condenser software)

Page 12: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 12/21

 

 Input values to Technisolve air cooled condenser software:

Barometer Pressure  (101.325 kpa) Type of Refrigerant (R134a)

On Coil Temperature (dpt,wbt) (380

C,340

C)

Condensing temperature (54.50C)

Air Volume (9.582 m3/s ) 

Air Velocity (3 m/s)

Fin Height (1118 mm) Target duty (150 Kw)

Number of Rows deep (6) 

Fin density (12 fpi)

Finned Length (2858 mm) Tube size (5/8 inch-38.1 ×50.8) 

Page 13: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 13/21

 

Techniso lve Condenser coi l Manufactur ing design procedure: 

1st Step: 

Page 14: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 14/21

 

2nd Step:

Page 15: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 15/21

 

3rd Step (Run Calculation from F9 button or button):

Model

Recoil (5/8 inch - 38.1x50.8)

1118 x 2858 6r 12f 11c

CD 15938 / 22 / 06 / 12.00 / 2858 Cu/GI (11)

Areas and VolumesAo = 628.104 m²

Ao' = 32.762 m²/face m²-rows

Ai = 19.285 m²

Vi = 75.3 Litre

Pipe ConnectionsSize = 35 mm

Heat Transferho = 71.064 W/m²°C

Ui = 1.616 kW/m²°CUo = 29.092 W/m²°C

 Ntu = 1.607

Cr = 0.000

Qt = e x Qmax

= 0.799 x 187.671 = 150.029 kW

Air Side DutyQt = ma (hao - hai)

= 10.672 (136.72 - 122.66) = 150.018 kW

Qs = ma x Cpa (dbo - dbi)

= 10.672 x 1.066 (51.2 - 38.0) = 150.029 kWRate = 15.651 kW/cms

Psychrometrics

Bypass factor = 0.020

Apparatus Dew Point = 33.1 °C

Refrigerant (R134a) DutySub-cooling = 5.0 °C

Mass flow = 0.827 kg/s (approx)

Mass flux = 1951.5 kg/sqm.s (approx)

Velocity = 1.809 m/sQt = mr x dh

= 0.827 x 181 = 150.029 kW

Dimensions

Height 1118.0 mm

Length 2858.0 mm

Depth 228.6 mm

Rows 6

Fins 12.00 fpi

Weight 775.7 kg

Page 16: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 16/21

 

CircuitingTubes High 22

Tube Count 132

Circuits 11

Circuit Basis Tubes high

Tubes/Circuits 12

Unlinked tubes 0

Serpentine 1/2

Eq Length 41.8 mConnections Same end

Tube (Staggered Pattern)ID 15.723 mm

OD 16.586 mm

Sx 38.100 mm

Sy 50.800 mm

FinThickness 0.200 mm

Area factor 1.000 mm

MaterialFin Cu

Tube Cu

Casing GI

Page 17: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 17/21

 

Psychrometric Chart:

Page 18: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 18/21

 

14.1.  Design of Air cooled condenser manually:

  Given Data 

(1)  

(2)  

(3) ⁄  (4)   *   

(5)  (6)  

Where   { ⁄ } 

 

 

⁄  

⁄ * 

Assume

 

 

ε=

 

 

 

 

 

 

 

Page 19: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 19/21

 

Afrontal = L × H = 3 ×1 = 3 

Assume   2.54  

 

 

Check on    

 

Tube side (ref.)

 

 

( )  

( )  

For air side 

By using induced draught far 

 

 

 

 

 

       

From tables

Page 20: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 20/21

 

[ ( )] 

(

)

 

 

 

    

Fin calculations

Assume  

 

⁄  

   

 

(

)

 

( ) 

 

From chart  

  

   

 

Page 21: Condenser & Evaporator

8/22/2019 Condenser & Evaporator

http://slidepdf.com/reader/full/condenser-evaporator 21/21

 

Assume w=15cm

   

 

 

 

   

 

 

  )