Design of An Innovative Refrigerated Display Cabinet

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Design of An Innovative Refrigerated Display Cabinet

Snehal Jadhav

Mechanical Engineering Vidyavardhinis College of Engineering and Technology

Vasai,India

Swapnali Panchal

Mechanical Engineering Vidyavardhinis College of Engineering and Technology

Vasai,India

Prajakta Kulkarni

Mechanical Engineering Vidyavardhinis College of Engineering and Technology

Vasai,India

Trupti Firake

Mechanical Engineering Vidyavardhinis College of Engineering and

Technology Vasai,India

Rishabh Melwanki Assistant Professor Mechanical Engineering VCET, Vasai, India

Dr. Uday Asolekar

Professor Mechanical Engineering

VCET, Vasai, India

AbstractAn innovative refrigerated display cabinet is an open refrigerator designed with a PVC curtain and air curtain.

This is acts as an artificial door between the cabinet and outside area. In this paper we have discussed the comparison between air curtain and PVC curtain. Due to transparency of PVC material customer can see the product and access the product. The purpose of using PVC strip curtain is to keep cabinet temperature between -2°Cto +6°C and food product temperature between 0°C to +6°Cwhere as air curtain, cabinet temperature can be obtained

+6°C to +9°C and food product temperature +12°C to +22°C. Thus it has been observed that electrical energy consumption including compressor power and fan power is to be 1.63KWh/day for air curtain and 1.12KWh/day for PVC curtain.

KeywordsPVC Curtain, Air Curtain

  1. INTRODUCTION

    In market, there are two types of refrigerators available according to their applications that is open refrigerated display cabinet and closed refrigerated display cabinet. An open refrigerated is most commonly used in big markets, malls and grocery shops. And the closed type refrigerated is having limited use for domestic purpose.

    1. Closed refrigerated display cabinet-

      A closed refrigerated is most widely used for domestic purpose. It is not used in supermarkets,malls because of more number of door opening frequency. An experimental study was performed to investigate the effect of operating conditions such as door opening frequency, product ambient temperature,volume occupied by the product, ambient conditions inside the closed refrigerated display cabinet. Due to higher door opening frequency the food product temperature inside the cabinet is affected[1].

    2. Open refrigerated display cabinet-

      Open type refrigerated is used in supermarkets because it has an extra use over the closed type refrigerated display cabinet. Feature of an open type refrigerated display cabinet is that it provides an ample space which is more than convenient to use. A night curtain is introduced when operating at night to enable power saving. CFD comparisons of open-type refrigerated display cabinets with/without air guiding strips result show that the air guiding strips decrease both the temperature of the chilled food products and the cooling capacity consumption [2].

      In the present paper, comparison between refrigerator enclosed with PVC strip curtain and air curtain has studied. In open type refrigerated display cabinet there is absence of door between the inside cabinet and warm ambient air. This type of arrangement gives easy access of food to the consumer to choose their product. Here, a refrigerator is designed with air curtain and PVC curtain which behaves similar to the door provided in the close type refrigerated display cabinet. It consists of two shelves including grill shelf and bottom panel where food products are kept. Either air curtain or PVC curtain is introduced for obtaining lower food product temperature. Usually open refrigerated display cabinet uses air curtain. The solution provided here use of PVC curtain in place of air curtain. Design presented below is of machine which can compare open display cabinet using air curtain and PVC curtain.

      1. Innovative refrigerator with air curtain-

        Air curtain is created in the front part of the refrigerator to avoid cooling loss and protect food products from surrounding heat. Air flows over evaporator coil to get cooled. This air forced up through the duct using three fans and flows vertically downward through honeycomb which act air curtain. Air curtain velocity was 0.3m/sand air curtain temperature was

        14°C. For cooling the cabinet, air is entering from backside perforated sheet to the cabinet area as shown in Fig1.

  2. DESIGN CALCULATION FOR PVC CURTAIN Calculation is done with the help of [3],[4],[5]

    Assumed

    Evaporator temperature = -5°C Condenser temperature = 62°C Hence, from Ph chart

    High pressure = 9.6 bar Low pressure = 2.66 bar

    p 414 KJ/kg

    p 448 KJ/kg

    h4 p 238 KJ/Kg

    Compressor capacity= 3 Ton

    4

    Fig.1. Innovative refrigerator with air curtain

    Qevp

    Qevp

    3 3.51

    4

    2.6325KW

    With the use of air curtain, cabinet temperature at the back side of the cabinet is found to be +6°C and in front, it is found to be

    +9°C.Cooling capacity is 2.4336KW.

      1. Innovative refrigerator with PVC curtain-

    Air curtain is replaced by PVC curtain. In this type of refrigerator air flow to honeycomb is completely stopped using damper so that air curtain is closed. This Poly Vinyl Chloride (PVC) curtain is highly stretchable and transparent in nature. Due to its transparency, customer can see the food product inside the cabinet and can access it.

    Energy Meter

    Energy Meter

    PVC

    Curtain

    PVC

    Curtain

    Fig. 2. Innovative refrigerator with PVC curtain

    This curtain is created in the form of strips. This completely closes the front part of the refrigerator. Therefore, it protects the food product temperature inside the cabinet from the atmosphere. With the use of PVC curtain, cabinet temperature at the back side of the cabinet is found to be -2°C to 0°C and

    Calculation of mass flow rate

    Qevap mr (p h4 )

    .

    2.6325 mr (414 238)

    .

    mr 0.0149 kg/sec

    .

    mr 53.84 kg/hr

    Calculation of heat transfer rate of compressor

    Qcomp mr (p p )

    Qcomp 0.0149(448 414)

    Qcomp 0.5066 KW

    Calculation of heat reject rate of condenser

    Qcond mr (p p )

    Qcond 0.0149(448 238)

    Qcond 3.129 KW

    Calculation of coefficient performance

    C.O.P Qevap

    Qcomp

    C.O.P. 2.3625

    0.5066

    C.O.P. 4.66

    1. Design of Evaporator

      1. Refrigerant side

        r

        r

        m A V

        v rv

        3 2

        at the front side of the cabinet it is found to be +3°C to +6°C. Cooling capacity is 2.6325 KW. Electrical energy consumption including compressor power and fan power is

        0.0149 12.071 (9 10 )

        4

        Vr = 19.40 m/s

        Vr

        calculated 1.6278KWh/day for air curtain and 1.118KWh/day for PVC curtain.

        Calculation of Reynolds number for heat transfer coefficient between the evaporator tubes

        v

        v

        Re = v D Vrv

        4.003103 4.819.402 12.071

        P 2 9103

        12.0719103 19.40

        Re =

        10.53106

        P 4849.54 Pa

        Re = 200.15103 ( hence Re > 4000 = Turbulent flow) Calculation of heat transfer coefficient for turbulent flow

        0.4

    2. Design of Condensor

      1. Refrigerant side

    Calculation velocity of liquid refrigernt in condenser

    Kv 0.8

    Cpv

    m AV

    hi = 0.023 D Re

    v

    K

    K

    v

    r l rl

    3 2

    3

    3

    h = 0.023 11.08510

    200.15103 0.8

    0.0149 1042.2 (9 10 )

    4

    Vrl

    i

    0.8755103

    9103

    0.4

    6

    Vr = 0.224 m/s

    Calculation of Reynolds number for heat transfer coefficient

    11.085103 10.5310

    between the condenser tubes

    2

    2

    hi 458.44 W/m K

    Re

    l D Vrl

    l

    1042.2 9103 0.224

    1. Evaporator tubes

      Re

      120.6106

      Re 17.42103 ( hence Re >4000 = Turbulent flow)

      Calculation of heat transfer coefficient for turbulent flow

      K C

      0.4

      h 0.023 l Re0.8

      i

      i

      pl

      l

      l

      D Kl

      65.2103 3 0.8 0.4

      65.2103 3 0.8 0.4

      hi = 0.023 17.4210 1.684 120.6

      9103

      2

      2

      hi = 648.55 W/m K

      1. Air Side

        65.2

        Fig. 3. Evaporator Tube

        Calculation of overall heat transfer coefficient

        Assuming air flowing at condenser be 400CFM and size of inlet air cabinet be of diameter 35cm

        .

        a

        a

        Q 400 CFM 0.1887 m3 /sec

        Uo As

        1

        1 1 1

        r

        A 0.352

        ln 2 4

        hi Ai hsi Asi 2 LKCu

        r1

        Considering fouling factor as 0.0002

        -3

        -3

        UO 1010 L

        A 0.0962 m2

        Inlet air velocity

        1

        1 0.0002 1

        5

        .

        V Qa

        458.44 9103 L 9 L 103 2 L 385 ln 4.5

        a A

        0.1887

        2

        2

        UO =377.74 W/m K

      2. Pressure drop in Evaporator

    Va 0.0962 1.96 m/sec

    DV

    f friction factor 0.046(Re)0.2

    Re a a

    a

    a

    a

    f 0.046(200.1510)0.2

    f 4.003103

    1.225 kg/m3

    and a

    1.81105 N-s/m

    fLV 2

    pressure drop P rv v

    Re

    1.2259103 1.96

    1.81105

    2D Re 1193.86

    K C

    0.333

    Width of fin (b) =200mm

    h 0.0683 a Re0.466

    a

    a

    pa

    a

    a

    D Ka

    Perimeter of fin (P) = 2×b y

    P = 2×(200×10-3 +350×10-3 )

    Cpa 1.005 KJ/kg

    P = 1.1 m

    Ka 0.024 W/mK

    Acs

    b y

    ha = 0.0683

    0.024

    10103

    1193.860.466

    Acs = 0.20.5

    1.0051.81105 103 0.333

    6 2

    Acs 10010 m

    0.024

    Number of fins on condenser

    h 4.05 W/m2K (from air side heat transfer coefficient)

    a

    a

    h 4.05 W/m2 K

    1. Condenser tubes

      P = 1.1 m (perimeter of fins)

      KAl 225 W/mK ( thermal conductivity of fins)

      l = 35010-3 m ( length of fin)

      For calculation heat transfer rate of fin Constant value for fin=m

      m ha P

      KAl ACS

      m =

      4.051.1

      225100106

      m = 14.07

      Qfin

      ha P KAl ACS ta – to tanhml

      Fig. 4. Condenser Tube

      Overall heat transfer coefficient

      ta

      to

      condenser outlet temperature evaporator outlet temperature

      UO As

      1

      1 1 1

      r 1

      4.051.1 2251104 (62 27) tanh(14.07 0.35)

      ln 2

      Qfin = 11.07 W

      (For 1 fin)

      hi Ai

      hsi Asi

      2 LKCu

      r1

      ho Aso

      Number of fins=140

      Considering fouling factor as 0.0002 (due to liquid refrigerant)and outer diameter as 10mm.

      3

      3

      UO 10 L 10

      1

      Qfin = 1551.19 W

      e) Pressure drop in condenser

      f 0.046(Re)0.2

      f 0.046 (17.42103 )0.2

      1 0.0002

      1 ln 5 1

      648.55 9103 L 9 L 103

      2 L 385 4.5 4.05 10103 L

      f 6.52103

      UO

      =4.01 W/m2 K

    2. Fins

      fLV 2

      Pressure Drop P rl l

      2D

      6.52103 19.2 0.224 1042.2

      Consider a single fin of size 200mm350mm and tube has external diameter of 10mm.

      P

      P 1623.58Pa

      2 9103

      Thickness of fins(y) =0.5mm No. of holes on fin=48

      Total area of fin=area of square-area of circle

  3. SELECTION OF EQUIPMENT

      1. Compressor –

        Hermetically sealed reciprocating compressor for refrigerant

        A

        (200 350) – 48( 102 )

        4

        R134a.

        Capacity- ¾ Ton Input power- 1700 W

        A 66230.0810-6 m2

        Input current- 7.9A

      2. Condenser

        Plate fin and tube type Air cooled condenser

        1. Material of tubes Copper Length of tube- 19.2 m

          Outer diameter 10mm Inner diameter- 9mm

        2. Fins

          Material of fins Aluminium No of fins 140

          Thickness of fins 0.5mm Length of fin- 350mm Width of fin- 200mm

      3. Evaporator

        Plate fin and tube type Air cooled evaporator

        1. Evaporator coil Material of tubes Copper Length of tube- 4.8 m Outer diameter 10mm Inner diameter- 9mm

        2. Fins

          Material of fins Aluminium No of fins 64

          Thickness of fins 0.5mm Length of fin- 101.6mm Width of fin- 101.6mm

      4. Expansion device Type capillary tube Material Copper

        Assumed dimensions using dan cap software

        Fig. 5. Selection of capillary tube using Dancap Software

        Length of tube 2.24m

        Diameter of tube- 0.80 mm

        Diameter of tube- 0.80 mm

        Actual dimensions Length of tube-203.2mm Diameter of tube-0.55mm

      5. Fan

        No of fans used-3

        No of fans used-3

        Dimensions 120×120×30mm Ac 220-240v

        Current 0.14A Frequency- 50/60Hz

      6. Honeycomb

    Honeycomb is used for laminar flow of air curtain.

    Dimensions- 500×50×50 mm

  4. CONCLUSION

    An innovative refrigerated display cabinet is designed, using PVC curtain and air curtain which acts as an artificial door between the cabinet and atmospheric air. This will helpful for reducing energy consumption by refrigerator.

  5. NOMENCLATURE

Symbol

Meaning

Unit

L

Length

m

b

Width

m

y

Thickness

m

A

Area

m2

P

Perimeter

m

t

Temperature

°C,K

V

Velocity

m/s

m

Mass flow rate

Kg/s

Q

Heat transfer

KW

h

Enthalpy of refrigerant

KJ/kg

density of refrigerant

kg/m3

Dynamic viscosity of refrigerant

N-s/m

v

Specific volume of refrigerant

m3/kg

cp

Specific heat at constant pressure of refrigerant

J/kgK

h

Heat transfer coefficient

W/m2K

K

Thermal conductivity of refrigerant

W/mK

Uo

Overall heat transfer coefficient

W/m2K

P

Pressure drop

Pa

r

Radius of tue

m

.

Qa

Volume flow rate

m3/s

f

Friction factor

PVC

Poly Vinyl Chloride

Subscript

Meaning

evap

evaporator

cond

condenser

comp

compressor

r

refrigerant

cs

cross section

i

Inner Side

o

Outer Side

l

liquid

v

vapour

a

air

1, 2, 3, 4

at point 1,2,3,4 resp.

s

Surface

Cu

copper

Al

Aluminium

Dimensionless numbers

Meaning

Re

Reynolds number

Pr

Prandtl number

Nu

Nusselt number

REFERENCES

  1. Denis Flick." Influence of operating conditions on the temperature performance of a closed refrigerated display cabinet", journal international of refrigeration,103(2019) 32-41.

  2. Jining Sun. CFD comparisons of open-type refrigerated display cabinets with/without air guiding strips, 1st international conference on sustainable energy and resource use in Food chains, ICEF 2017, 19-20 April 2017, Berkshire, edition (2017) 54-61.

  3. KuppanThulullanam, Heat Exchanger Design Handbook,2nded.BocaRaton:CRC Press,2013.

  4. R.K.Rajput,Heat and Mass Transfer,5thed.S Chand and company, 2012.

  5. R. S. Khurmi, J. K. Gupta,Refrigeration and Air Conditioning,5thed.S Chand and company,2012.

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