Post on 22-Jul-2015
A Project report by,
Vijay Aravind . AVishnu D.S.Vishaal. G
Under the guidance of
MAHBOOB E. AFSHAN
Senior Grade professor Department of Mechanical Engineering
B. S. Abdur Rahman University.
Heat Transfer Analysis by Stratification of
HDPE encapsulated HS89(PCM)
• Solar energy is receiving a lot of sustainable energy and is used for power
generation and other applications. A major limitation is that it is available
only about 2000hrs a year in many places. Therefore it is critical in order to
store the thermal energy in off hours.
• Sensible heat have been storing energy but due to material properties this
type of storage have its limitations too.
• Using Encapsulated Phase change materials is potentially a better way to
store thermal energy with the associated reversible heat transfer.
• By storing the Latent heat energy into the Phase change materials by natural
heating and storing for a particular off hours, and releasing this heat energy
when required is the main objective of our project.
• Each site could be made as SMART GRID by this method of power storage.
• Greater power saving method by controlled heat emission by our requisites.
• Stand-By Capacity - in case the main machinery fails, the stored energy can
be utilized to handle the system loads, thereby providing a degree of back-up
facility.
• Flexible System - the overall machinery capacity and TES capacity can be
exactly matched to system loads.
• Reduced Machinery and reduced running cost - shifting some of the peak
load may enable designers to reduce the main machine size.
• Green Solution - reduced machinery size means reduced energy
consumption, giving lower direct and indirect CO2 emissions.
• The overall energy rate is heavily decreased considering the per annum
decrement of the energy consumption of the working machinery therby
reducing the cost.
There are several methods to store Thermal energy and are us follows :
Sensible Heat Storage Method
Latent Heat Storage Method
Chemical Heat Storage Method
Thermosyphon method- to achieve steam in the collectors
Stratification method
Cascading of the Phase Change Materials.
HTF from the solar heater
Cylindrical tank
Heat absorbed
by the pcm
HTF collected
at the bottom of the tank
HTF pumped
back
Choosing HS 89 as the Phase Change Material
HS 89 is an inorganic chemical based Phase Change Material with a
melting temperature of 89ᴼC. It stores thermal energy as latent heat in
its crystalline form. On changing its phase, this latent heat is released or
absorbed, allowing the ambient temp within the system to be
maintained. HS 89 is constituted to the right mix of various salts,
additives and nucleating agents allowing equilibrium between solid and
liquid phases to be attained at the melting point. While melting, it
continues to absorb heat from the environment without further increase
in temperature, thereby maintaining the system temperature.
It is non-flammable.
HS 89 is chemically and thermally stable.
HS 89 has a freezing temperature of 85ᴼC, a temperature that makes it
suitable for many storage applications.
The setup basically consists of four sections:
Heater setup
Thermal Energy Storage tank
Centrifugal Pump
Data Acquisition System
Heater setup :
The heater setup is a stainless steel tank of 360mm
diameter and 530mm height. Its capacity is 55lts. In the
bottom of this tank a 3000W immersion heater is attached
which will heat the HTF simulating the temperature of a
solar collector. To the immersion heater, a thermostat is
attached to the bottom which will control the temperature
ensuring that constant temperature is maintained in the
bath. The heater setup tank is insulated by glass wool to
prevent heat losses. The heater setup and TES tank are
connected by means of flexible steel hose and GI pipes.
Thermal Energy Storage tank :
The TES tank consists of PCM (HS 89) balls which are
packed in four layers. The bottom layer is left empty
to provide easy suction for the pump. Each layer in
the TES tank contains 11 balls each. The TES tank
contains 44 HS 89 balls in total.
Each of the layers is surrounded by a wire mesh. On
the top of the TES tank, a distributor plate of
circular cross section is placed to ensure that the
HTF falls uniformly on each ball in the different
layers. In each layer of the TES tank, a J-type
thermocouple is drilled into it to note the
temperature variation. The TES tank is insulated
using polyethylene foam to prevent heat losses.
Centrifugal pump :
The centrifugal pump is used to re-
circulate the HTF(heat transfer fluid)
leaving the TES tank back to the
heater setup tank. It is a mono-block
pump and it has a head of 15m.
Data Acquisition System :
The Data acquisition system consists of a NI-
9213(National instrument) for recording
temperatures from the thermocouples from
each layer of the TES tank. The temperatures
are measured using the LABVIEW software
and the data acquired is read onto the
computer from the NI-9213 instrument and
temperature readings are recorded for every
minute of the run.
Drilling: Drilling is a cutting process that uses a drill bit to cut or enlarge a hole of
circular cross-section in solid materials. The drill bit is a rotary cutting tool, often multipoint. The bit is pressed against the workpiece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the workpiece, cutting off chips from what will become the hole being drilled
In the fabrication process,4mm holes were drilled in the nuts of the HS 89 balls so as to place the thermocouples inside and several holes were drilled in the distributor plate to enhance the flow rate of heat transfer fluid.
Brazing:Brazing is a metal-joining process whereby a filler metal is heated above melting
point and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting (liquidus) temperature while protected by a suitable atmosphere, usually a flux. It then flows over the base metal (known as wetting) and is then cooled to join the workpieces together. It is similar to soldering, except the temperatures used to melt the filler metal are higher.
In the fabrication process, the thermocouples are brazed along with the nuts of the HS 89 balls to prevent HTF entering into the PCM.
Soldering:Soldering is a process in which two or more metal items are joined together by
melting and flowing a filler metal (solder) into the joint, the filler metal having a lower melting point than the work-piece. Soldering differs from welding in that soldering does not involve melting the work pieces. In brazing, the filler metal melts at a higher temperature, but the work-piece metal does not melt.
In the fabrication process, we have soldered the immersion heater in the stainless steel tank to prevent any leakages.
S.
NOBILL OF MATERIALS QUANTITIY AMOUNT
(In Rs)
1 HS-89 BALLS
2 THERMOFOAM
3 SHEET METAL
4 J-TYPE
THERMOCOUPLE
6 900
5 THERMOCOUPLE PIN 26 400
6 ROTOMETER 1
7 DAQ (NI-9213) 1
8 CENTRIFUGAL PUMP 1
9 ENERGY METER 1
10 DISTRIBUTOR PLATE 1
11 TES TANK(1:3) 1
12