Ex No:
Date:
AGITATED VESSEL
AIM:
To obtain the overall heat transfer coefficient (U) for heating and cooling of vessel
contents, with fluid flowing in a tubular coil, undergoing sensible heat change.
APPARATUS DESCRIPTION:
The set up consist of a SS 304 Tank with proper electrical heater and is insulated from
outside. A suitable cooling coil is provided inside the tank. An agitator with a variable speed
drive is provided. Cooling water temperature and tank temperature can be measured by
thermometer placed in the thermowells. Four number of baffles are provided in the tank.
Tank is provided with a water charging line.
TECHNICAL SPECIFICATIONS:
Cylindrical Tank:
Volume:
25 liter (approx.)
Inside Diameter: 300 mm; Height: 450 mm; MOC: SS 304
Cover is fitted to the vessel with four stud type bolts (10 mm threading) of SS 304L for easy
opening.
Baffles:
4 Nos.
Thickness: 3 mm;
Length: 425 mm; Width: 15 mm
Insulation:
Glass Wool
Thickness: 25 mm; Foil: SS 304 on insulation
Drain Valve:
½”
Vent Cock:
½”
Heater:
6 kW
Cooling Coil:
Inner Diameter:
10 mm;
Outer Diameter: 12 mm; No. of Turns: 11; MOC: SS
Agitator:
Type: Turbine Type
Diameter: 100 mm; Shaft Dia.: 10 mm
Shaft Length: 400 mm (approx.)
Motor:
Motor Type: Gear Type; RPM (max.): 232; Rated Power Consumption
: 0.25 kW
Rotameter:
Glass tube
: borosilicate glass
Range
: 2.5 – 25 LPM
Qty
: 2 Nos.
Control Panel:
 Digital temp. indicator with selector switch (6 zones)
 Digital PID controller
 On / off switch for water pumps
 On / off switch for water heaters
 Mains
THEORY:
A simple jacketed pan or kettle is very commonly used in the chemical industries as a
reaction vessel. In many cases, such as in nitration or sulphonation reactions, heat has to be
removed or added to the mixture in order either to control the rate of reaction or to bring it to
completion. The addition or removal of heat is conveniently arranged by passing steam or
water through a jacket fitted to the outside of the vessel or through a helical coil fitted to the
inside. In either case some form of agitator is used to obtain even distribution in the vessel.
This may be of the anchor type for very thick mixes or a propeller or turbine if the contents
are too viscous.
In this case, the thermal resistances to heat transfer arise from the water film on the
inside of the coil, the wall of the tube, the film on the outside of the coil, and any scale that
may be present on either surface.
By making energy balance, we get
In the above equation,
U = overall heat transfer coefficient
A = heat transfer area
T = temperature of tank contents
Tc = average temperature of cooling / heating fluid
m = mass of tank contents
CP = specific heat of tank contents
t = time duration since the start of fluid flow in the coil
Assuming, U to be a constant, and taking an average value of Tc for the total duration of the
experiment, we can integrate the above expression, as below:
In the above equation,
T1 = temperature of tank contents at t = 0
T2 = temperature of tank contents at t
Procedure:
 The agitated vessel is filled with known amount (20 litre) of water (about 70-75%
height of the vessel).
 The stirrer is started and the RPM is maintained throughout the process.
 The heater is switched on and water in the reservoir is heated to the desired
temperature (about 60°C).
 The temperature of bulk water is measured periodically with the help of the
thermocouple.
 Now, the hot water supply in the coil is started and its inlet and outlet temperatures
are measured periodically with thermocouple which is indicated on the control panel.
 The values of bulk water temperature, hot water inlet and outlet temperatures and hot
water flow rate are noted.
 The hot process fluid is kept in the vessel for further cooling process.
 The process for heating is repeated for cooling and the corresponding temperatures
are noted.
OBSERVATIONS:
Heating:
°C
Bulk Water Temperature in the vessel at the start =
Hot Water Flow Rate (mw) =
LPM =
kg/s
°C
Coil Water Inlet Temperature =
Cooling:
°C
Bulk Water Temperature in the vessel at the start =
Cold Water Flow Rate (mw) =
Coil Water Inlet Temperature =
LPM =
kg/s
°C
OBSERVATION:
Heating Cycle:
Average
Temperature
Time since start of flow of
Temp of Tank
Temperature of coil
of coil
coil fluid
Contents
outlet
contents
(min)
o
C
0
o
C
-
o
C
-
Average temperature of coil contents over the entire duration
Cooling Cycle:
Average
Temperature
Time since start of flow of
Temp of Tank
Temperature of coil
of coil
coil fluid
Contents
outlet
contents
(min)
o
C
o
C
0
Average temperature of coil contents over the entire duration
o
C
CALCULATIONS:
Length of coil = π x d x n = π x 0.012 x 11 = 0.414 m
Area of coil Acoil = π d l = π x 0.012 x 0.414 = 0.0156 m2
For Heating Cycle:
From the above table,
Tc =
_________
o
T1 =
_________
o
T2 =
_________
o
t=
_________ s
C
C
C
W/m2.oC
U from formula as above:
For Cooling Cycle:
From the above table,
Tc =
_________
o
T1 =
_________
o
T2 =
_________
o
t=
_________ s
U from formula as above:
C
C
C
W/m2.oC
RESULT:
An experiment on agitated vessel was conducted and the overall heat transfer
coefficient for heating was found to be ------kW/m2.0C and for cooling was found to be ----kW/m20C.