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Impact of Fouling on VCRS and its experimental study

Guided By: Submitted by:Mr. Ankit Kulshreshtha(Project Guide) Piyush Kumar(1101440033) Rishabh Pandey(1101440040) Shantanu Kaushik(1101440051) Shashank Pandey(1101440052)

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CONTENTS

TopicsTest rigExperimental Setup DescriptionProperties of RefrigerantActual CycleLosses in VCRSMathematical CalculationsVariation of COP with different

parametersComparison of ResultsFouling MitigationConclusionReferences

Page No.34-910-12131415-2021-32

3334-3536-3738

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Fig No. 1 Refrigeration Test Rig [6]

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Experimental setup description[6]

1-Thermocouples: Six thermocouples are used in our test rig. The readings of the thermocouples are taken by knob by rotating it .first thermocouple fit at outlet of the condenser. Second and third thermocouples are fitted in the condenser tank and evaporator tank respectively. And remaining thermocouples are fitted in inlet water tank, inlet to condenser and outlet to evaporator.

2-Condenser and evaporator: - as shown in the figurethe tub and tube type condenser and evaporator are used in the kit and the evaporator having insulator on it. These tanks contain the two mechanicalagitators as shown in figure, for the continuous mixture the water,the agitator can be controlled by switch . These tanks have two valves at the lower side of tanks for the water outlet. A copper tube is used for the flow of the refrigerant in spiral form in the tub.

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Fig No.2 Condenser[6]

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Experimental setup description:-

3-Display devices: our refrigeration test-rig contains LED type display device. All the readings are shown through these display devices.

4-Stirer: A stirer is used for the proper mixing of water and to maintain the temperature uniformity throughout the tank and it is of 1 to 70 hp and 45 watt, 50 Hz and 230 Volt.

5-Rotameter and water tank: rota meter is fitted in between water tank and the condenser and evaporator tank and it contains a motor that is used to raise the pressure of the water and it contains a switch by which the flow of water can be controlled.

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Fig No.3 Evaporator[6]

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Experimental setup description:-

6-Expansion valve,compressor and drier: in our refrigeration test-rig a reciprocating compressor is used to compress the refrigerant before condenser and it is placed between the evaporator and condenser and it is of 230 volt,50 Hz and single phase. The drier is used to absorb the moisture content and it is placed between the inlet to evaporator and outlet to the condenser. A copper capillary tube type expansion device is being used for the expansion of the refrigerant and it is placed between drier and evaporator.

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Experimental setup description:-

7-Pressure gauges: – The two pressure gauges are used , one at high pressure side and other one is placed at the lower pressure side to measure the condenser pressure and evaporator pressure respectively. Means one is suction pressure gauge and other one is discharge pressure gauge, suction pressure gauge having pressure range from 0 to 150 psi and discharge pressure gauge having pressure range from 0 to 300 psi.

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Properties of the refrigerant-

Molecular weight: 102.03 g/mol.

Critical point• Critical temperature: 100.95 °C• Critical pressure: 40.6 bar • Critical density: 512 kg/m3

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Properties of the refrigerant-

Liquid phase• Liquid density (1.013 bar and 25 °C (77 °F)) : 1206 kg/m3

• Boiling point (1.013 bar) : -26.55 °C• Latent heat of vaporization (1.013 bar at boiling point) :

215.9 kJ/kg• Vapor pressure (at 20 °C or 68 °F) : 5.7 bar• Vapor pressure (at 5 °C or 41 °F) : 3.5 bar• Vapor pressure (at 15 °C or 59 °F) : 4.9 bar• Vapor pressure (at 50 °C or 122 °F) : 13.2 bar

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Properties of the refrigerant-

Gaseous phase• Gas density (1.013 bar at boiling point) : 5.28 kg/m3

• Gas density (1.013 bar and 15 °C (59 °F)) : 4.25 kg/m3

• Compressibility Factor (Z) (1.013 bar and 15 °C (59 °F)) : 1

• Specific gravity : 3.25 • Specific volume (1.013 bar and 15 °C (59 °F)) : 0.235

m3/kg

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Fig No.4 ACTUAL VAPOR COMPRESSION CYCLE [5]

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Fig No.5 Schematic diagram of a simple refrigeration cycle and various losses in VCR system. [5]

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MATHEMATICAL CALCULATION [6]

1.Expansion valve: h6 = h7 , at P1 and T1, h1 = 297.1 kJ/kg from table,

at T6 = 40.8 and P6 = 1040 kPa , h6 = 109.7 kJ/kg from table,

pressure loss in condenser = P1 – P6

= 1385.4 – 1040 = 345.4 kPa. Ploss

cond = 25% of Pc

h6 =h7 = 109.7 kj/kg

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MATHEMATICAL CALCULATION[6]

2.Evaporator :- T7 = -6.90C, h6 =h7 = 109.7 kj/kg, P7 = 225.6 kPa

h7 = hf + x hfg at 225.6 kPa

109.7 = 42.51 + x(246.32 – 42.51)x = 0.329T4 = 10.30C, Pe = P4 = 170 kPa , h4 = 262.0 kJ/kg

Pressure loss in evaporator = P7 – P4 =55.6 kPa

Plossevap = 25% of Pevap

(Qevap) R = mR ( h4 – h7) = 0.008 (262 – 109.7) = 1.218 kW

(Qevap) W = mW.CPW . ( Two – Twin) = mw.Cpw (T5 –T3)

= 0.046 Х 4.186 (18.3 – 12.4) = 1.134 kW

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Qlosss= 1.218 – 1.134 = 0.08 approx 5% of Qevap

(Qmax)evap = mW.CPW ( Twine – Trine )

= mW.CPW ( T5 – T7 ) = 0.046 Х 4.186 (18.3 + 6.9) = 4.84 kW

Ɛ = (Qevap)w / Qmax = 1.134 / 4.84 = 0.23 = 23%.

Ɛ = (Qevap)R / Qmax ) = 1.218 / 4.84 = 0.25 = 25%.

Qlosss = mR ( h4 – h7) - mW.CPW . ( Two – Twin)

Refrigeration effect = mR ( h4 – h7) - 0.05 mR ( h4 – h7) = 1.134 kW

Now, Ɛ = 1 – exp(-NTU)NTU = UA / Cmin

UAe = Cmin. ln(1/ 1 - Ɛ evap)

U = (mW.CPW /Ae) ln(1/1-0.23)

U = ( 0.046 Х 4.186)/0.6619 ln(1/0.77)U = 75.69 watt/m2 0C.

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MATHEMATICAL CALCULATION:

3.Compressor:h4 = 262 kJ/kg and S4 = 1.010 kJ/kgK

at 1385.4 = Pb = Pc , Sg = 0.9108 kJ/kgK

since, Sg< S4 hence point lies in the superheated region.

At1385.4 kPa, Sb = 1.006 kJ/kgK at 800C, hb = 308.4 kJ/kg

Ƞ = 0.72 , ƞisentropic = hb – h4 / ha – h4

ha = 262 + (308.4 – 262) / 0.72

= 326.44 kJ/kgAt 326.44 kJ/kg , P = 1385 kPa and T = 920C

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MATHEMATICAL CALCULATION:

Heat loss in compressor :mR( h4 - ha) - mR( h4 – hb) = 0.008 (326.44 – 262) – 0.008(308.4 – 262)

= 0.144 kWQloss

discharge + Qlosscomp = mR( h1 - ha) = 0.008(326.44 – 297.1) = 0.234

kWQloss

discharge = 0.234 - .144 = 0.09 kW

(Wcomp)actual = mR (ha - h4) = 0.008 (326.44 – 262) = 0.515 kW

(Wcomp)isentropic = mR (hb - h4) = 0.008(308.4 – 262) = 0.371 kW

COP = RE / Wcomp = 1.134 / 0.515 = 2.2

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MATHEMATICAL CALCULATION:

4.Condenser:(Qcond)w =mW.CPW . ( Twoc – Twinc) = 0.046 Х 4.186 (26 – 18.3)

= 1.48 kW(Qcond)R = mR (h1 – h6) = 0.008(297.4 – 109.7) = 1.49 kW

Qmax = mW.CPW (69.1 – 18.3) = 9.76 kW

Ɛcond = (Qcond)w / Qmax = 1.48 / 9.76 = 0.1516i.e. 15.16%

Now, Ɛ = 1 – exp(-NTU)NTU = UA / Cmin

UAc = Cmin. ln(1/ 1 - Ɛcond)

U = (0.046 Х 4.186) / 0.3301.ln(1/1-0.15)U = 94.66 watt/m2 0C

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VARIATION OF COP, REFRIGERATION EFFECT AND COMPRESSOR WORK WITH MASS FLOW RATE:-

Input

variables

RE Wcomp COP UCond Uevap

mw1

0.046(kg/s)

1.134 kW 0.515 kW 2.04 94.66

(w/m2 0C)

75.69

(w/m2 0C)

mw2

0.07(kg/s)

1.002 kW 0.552 kW 1.80 144

(w/m2 0C)

115.7

(w/m2 0C)

mw3

0.09(kg/s)

0.990 kW 0.672 kW 1.47 185

(w/m2 0C)

148.7

(w/m2 0C)

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Fig No.6 Graph (Mass flow rate vs COP)

COP

Mass flow rate of water (kg/s)

0.046 0.07 0.09000000000000010

0.5

1

1.5

2

2.5COP

COP

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Fig No.7 Graph (COP vs Ucond)

COP2.04 1.8 1.47

0

20

40

60

80

100

120

140

160

180

200

Ucond (w/m2 0C)

Ucond (w/m2 0C)

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Fig No.8 Graph (COP vs Uevap)

COP

2.04 1.8 1.470

20

40

60

80

100

120

140

160 Uevap (w/m2 0C)

Uevap (w/m2 0C)

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Fig No.9 Graph (Mass flow rate of water vs Refrigeration Effect)

Mass flow rate of water (kg/sec)

0.046 0.07 0.090.9

0.95

1

1.05

1.1

1.15

REFRIGERATION EFFECT (kW)

REFRIGERATION EFFECT (kW)

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Fig No.10 Graph (Compressor Work vs COP)

Compressor work (kW)

0.515 1.002 0.990

0.5

1

1.5

2

2.5

COP

COP

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Fig No.11 Graph (COP vs Wcomp)

COP2.04 1.8 1.47

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Wcomp (kW)

Wcomp (kW)

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Fig No.12 Graph (Mass flow rate of water in condenser(kg/sec) vs COP)

COP

Mass flow rate of water in condenser(kg/sec)

0.028 0.046 0.052 0.0660

0.5

1

1.5

2

2.5

3

3.5

4

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Fig No.13 Graph (Compressor work(watt) vs COP)

COP

Compressor work(watt)

208 245 266 3080

0.51

1.52

2.53

3.54

04/15/2023 30Fig No.15 Graph (Condenser pressure(bar) vs COP)

COP

Condenser pressure(bar)

9.3 10.3 10.8 11.40

0.5

1

1.5

2

2.5

3

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VARIATION OF COP WITH TEMPERATURE:

Input temperature (TWinc) (0C) COP

21.2 2.7

25.2 2.47

28 2.04

28.7 1.88

04/15/2023 32Fig No.16 Graph (Input Temperature vs COP)

COP

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COMPARISON BETWEEN MATHEMATICAL AND EXPERIMENTAL RESULTS:INPUTS MATHEMATICAL

RESULT

EXPERIMENTAL

RESULT

ERROR

( %age)

T1 (0C) 70 69.1 1

T6 (0C) 41 40.8 0.5

T7 (0C) -7 -6.9 1

T4 (0C) 10 10.3 2

COP 2.2 2.04 7

RE (kW) 1.134 1.134 0

Wcomp (kW) 0.515 0.555 7

Ucond (watt/m2 0C) 94.66 94.66 0

Uevap (watt/m2 0C) 75.69 75.66 0

Twoe (0C) 12 12.4 3

Twoc (0C) 26.14 26 0.5

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Fouling Mitigation

Offline techniques clean heat exchangers by mechanical and/or chemical means while the system is down, which results in lost production time. They are labor-intensive and expensive; as much as 8% of the maintenance costs in a typical industrial plant are due to fouling mitigation in heat exchangers. When offline mitigation requires the use of aggressive chemicals, the company is saddled with additional operating costs, and new problems relating to the increased safety hazards for company personnel and disposal of toxic waste. Moreover, the fouling process starts again immediately after cleaning, and the gradual accumulation of deposits reduces performance until the next cleaning treatment is initiated. These drawbacks make heat exchanger operation with regular offline cleaning expensive, cumbersome and inefficient for the entire industrial process.

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Fouling Mitigation

The online method is an ongoing process which uses mechanical means to keep the heat exchanger clean while it operates. Some cleaning systems also use chemicals (which must be carefully adapted to each process), but online mechanical-only cleaning is

both environmentally responsible and highly cost-effective.Online mechanical cleaning boosts performance in two ways: it

does not require system shutdown with temporary loss of operation; and it keeps performance optimal and energy-efficient through continuous cleaning, which does not allow any fouling to occur. In addition, online mechanical cleaning does not only eliminate staff time for cleaning services, but also purchase of chemicals and waste disposal.

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CONCLUSION:-

We have successfully validated the performance of VCR system with the help of our mathematical model and we have also studied the effect of various parameters like mass flow rate of water, condenser pressure, evaporator pressure, input temperatures in condenser and evaporator,etc on the COP and vapor compression refrigeration system.

We have also study the fouling phenomenon in the condenser and evaporator of VCR system.After drawing the curves among various parameters we conclude that:

1) As mass flow rate of water increases the COP of VCR system decreases.2) As overall heat transfer coefficient of evaporator increases the COP of

the VCR system decreases.3) As overall heat transfer coefficient of condenser increases the COP of

the VCR system decreases.

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CONCLUSION:-

4) As mass flow rate of water increases the refrigeration effect decreases.

5) As compressor work increases the COP of the VCR system decreases.6) As the condenser pressure increases the COP of the VCR system

decreases.7) As the evaporator pressure decreases the COP of the VCR system

decreases.8) As the input temperature increases the COP of the VCR system

decreases.

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References

1.Cabello, R., Navarro, J., & Torrella, E. (2005). Simplified steady-state modelling of a single stage vapour compression plant. Model development and validation.Applied thermal engineering, 25(11), 1740-1752.2.Qureshi, B. A., & Zubair, S. M. (2012). The impact of fouling on performance of a vapor compression refrigeration system with integrated mechanical sub-cooling system. Applied Energy, 92, 750-762.3.Qureshi, B. A., & Zubair, S. M. (2014). The impact of fouling on the condenser of a vapor compression refrigeration system: An experimental observation.International Journal of Refrigeration, 38, 260-266.4.Cabello, R., Torrella, E., & Navarro-Esbr , J. (2004). Experimental evaluation of a ı́ �vapour compression plant performance using R134a, R407C and R22 as working fluids. Applied thermal engineering, 24(13), 1905-1917.5.Arora,C.P. (2014) , Actual Vapour Compression Refrigeration Cycle. Refrigeration and Air Conditioning, 114-1156. Katiyar,C.,Yadav,A.,Singh,R.P.,Soni,R.K. & Awasthi,Hrydesh.(2014), Impact of Fouling

on VCR System.