NAME 430 – Marine Engineering Sessional (Lab Sheet) Experiment – 04: Study and Performance Test of a Refrigeration Unit

Prepared by – Md. Habibur Rahman, Lecturer (Dept. of NAME), BUET 1 | P a g e

01. Name of the Experiment: Study and Performance Test of a Refrigeration Unit.

02. Write down the objectives of this experiment.

03. Specifications & Ambient Data

Model

Type of refrigerants

Power input

Compressor side maximum pressure

Suction side minimum pressure

Type of transducer used for measuring temperature

Compressor Type

Sub-cooling availability

Super heating availability

04. A system diagram of the Refrigeration unit along with its performance test set-up is shown

below - - -

Prepared by – Md. Habibur Rahman, Lecturer (Dept. of NAME), BUET 2 | P a g e

Data Sheet

A. Observation Table

Start the refrigerating unit and allow some time to bring it to steady state condition. Then

take temperature, pressure readings at different state points (as available). Measure flow

rates of refrigerant and condenser water.

Wa

tt

Met

er

Ice

Ca

n

Tem

p.

T9

(˚C

)

Bri

ne

Ev

ap

ora

tor

Tem

p. Ou

t

T6

(˚C

)

In

T5

(˚C

)

Cooli

ng

wate

r

Con

den

se

r T

emp

.

Ou

t

T8

(˚C

)

In

T7

(˚C

)

Flo

w r

ate

of

ref.

(liq

)

(L/m

in)

Evap

.

Ou

tlet

Tem

p.

(R-1

2)

T4

(˚C

)

Con

d.

Ou

tlet

Tem

p.

(R-1

2)

T3

(˚C

)

Com

p.

Sp

eed

(r.p

.m.)

Co

mp

ress

or Tem

per

atu

re

Del

iver

y

Tem

p.

T1

(˚C

)

Su

ctio

n

Tem

p.

T1

(˚C

)

Pre

ssu

re

Del

iver

y

Pre

ssu

re

P2

(kg

/cm

2)

Su

ctio

n

Pre

ssu

re

P1

(kg/c

m2)

Per

iod

Prepared by – Md. Habibur Rahman, Lecturer (Dept. of NAME), BUET 3 | P a g e

Table – 01

Point Temperature (˚C) Enthalpy (kJ/kg)

Table – 02

No. of

Obs.

Refrigerant Water

Flow rate Suction sp.

Volume

(m3/kg)

Flow rate

(kg/s)

Temperature

L/min Kg/hr Inlet (˚C) Outlet (˚C)

Table – 03

No. of

Obs.

Volumetric

Effeciency

𝛈𝐯 (%)

Heat rejection capacity, 𝐐𝐂 Refrigerant

effect

𝐐𝐄 (kW)

Coefficient

of

Performance

(COP)

Based on

cooling

water (kW)

Based on

enthalpy of

refrigerant ( kW)

Prepared by – Md. Habibur Rahman, Lecturer (Dept. of NAME), BUET 4 | P a g e

B. Sample Calculation

a. Volumetric efficiency of the compressor,

ηv =mr × vr

60 × nVP

where,

mr = Flow rate of refrigerant (kg/h)

vr = Sp. Vol. of refrigerant corresponding to suction state of compressor (m3)/kg

n = Rotational speed of compressor (rpm)

VP = Total cylinder displacement (m3) [consider as 2.57×10-4 m3]

b. Heat Rejection Capacity of Condenser

i. Based on heat extracted by condenser cooling water

QC = Cw × mw × (T8 − T7) kW

where,

Cw = Specific heat of water (4.187 kJ/kg – deg.C)

mw = Flow rate of cooling water (kg/s)

ii. Based on enthalpy of refrigerant

Qc =mr × (h2 − h3)

3600 kW

where,

h2 = Enthalpy of refrigerant corresponding to delivery condition of the compressor

(kJ/kg)

h3 = Enthalpy of refrigerant corresponding to outlet condition of the condenser

(kJ/kg)

c. Refrigerating Effect

QE =mr × (h1 − h4)

3600 kW

where,

h1 = Enthalpy of refrigerant corresponding to suction state of the compressor (kJ/kg)

h4 = Enthalpy of refrigerant corresponding to outlet state of expansion valve (kJ/kg)

d. Coefficient of Performance

COP =h1 − h2

h2 − h1

e. kW/Ton = (Reading of watt meter/Refrigerant effect in Tons)

f. Flow rate (𝐦𝐫) of refrigerant based on flow meter

mr = ρT(F2 − F1)60/t where,

ρT = Density of refrigerant (kg/I)

F1 = Initial flow meter reading before starting stop watch (I)

F2 = Final flow meter reading at the point of stopping of stop watch (I)

t = time in minute

Prepared by – Md. Habibur Rahman, Lecturer (Dept. of NAME), BUET 5 | P a g e

C. Assignments

Inspect the unit and answer the following - - -

a. What is the type of condenser?

b. What is a solenoid valve and why is it used?

c. What is the purpose of using a sight glass?

d. Why liquid to suction gas heat exchanger is used?

e. What are the functions of an expansion valve? What type of expansion valve is used

here?

f. Why brine tank is insulated?

g. Why high pressure & low pressure switches are used in refrigerating system?

h. What is the speed of the motor and what is the number of poles of the motor?

i. What are the functions of an Air Handling Unit (AHU) and a Fan Coil Unit (FCU)?

D. Discussion

Discuss the above study and express your comments regarding the experiment.