Novel Design of a Portable Heat Energy Storage Device Adopting a Phase Change Material for CHP and...
-
Upload
shaniya-ratcliff -
Category
Documents
-
view
218 -
download
4
Transcript of Novel Design of a Portable Heat Energy Storage Device Adopting a Phase Change Material for CHP and...
Novel Design of a Portable Heat Energy Storage Device Adopting a
Phase Change Material for CHP and Solar Energy Applications
K. TRAPANI
BSc. Renewable Energy Final Year Dissertation
Project Supervisor: Dr. Dean Millar
INTRODUCTION
Concept: Extraction of waste heat
from an automotive micro-CHP engine using a portable
thermal storage device (Millar & Huang, 2009)
Specific design of the portable thermal energy storage adopting phase
change materials (PCMs)
•Compact•Light
•Modular•Stackable
•High thermal energy storage•Efficient heat transfer
REQUIREMENTS OF THE DEVICE
PORTABILITY
FLEXIBLE THERMAL CAPACITY
MAXIMISED PERFORMANCE
DEVICE DESIGN
Modular unit:Mass = 15kgDimensions = 20cm x 35cm x 18cm
Model unit (1/5th scale):Mass = 3kgDimensions = 12cm x 35cm x 6cm
Component Material
PCM Paraffin waxPiping CopperFins Aluminium
Internal case SteelInsulation Reflective foam
External case Plastic
SOLIDWORKS DESIGN OF A 1/5th SCALE MODEL
PCMs – materials which exhibit a phase change (from one state to another)
PHASE CHANGE MATERIALS (PCMs)
STATES
GAS
LIQUID
SOLID
Enth
alpy
of S
yste
m
TEM
PERA
TURE
ENTHALPY
SOLID
LIQUID
GASPHASE CHANGE
PHASE TRANSITIONS
SELECTION OF DEVICE’S PCM
SOLID-LIQUID
SOLID-SOLID
SOLID-GAS
GAS-LIQUID
SOLID-LIQUID
ORGANICS INORGANICS• Not corrosive• Low or no undercooling• Chemically and thermally ostable
• Greater phase change oenthalpy
Paraffin Wax
Relatively high heat of fusion
Stable heating and cooling cycle
Economical and abundant
PROPERTIES OF THE DEVICE’S PCMDensity, ρ (solid) 896 kg/m3
Density, ρ (liquid) 820 kg/m3
Melting temperatures, T 328K – 330K
Specific heat capacity, cs 3412 J/kgK
Specific heat capacity, cl 4466 J/kgK
Latent heat of fusion, L 197 kJ/kg
0 500 1000 1500 2000 2500 3000 3500 40000
10
20
30
40
50
60
Time (s)
Tem
pera
ture
(deg
C)
Where Q = Pt
Governing equations:
Q = mc∆ϴ
Q = mL
Sensible heating
Latent heating
SIMULATION
Simulation software had to be modelled to account for the phase change material.
Assumptions:• Paraffin wax is homogenous and isotropic• Heat is transferred only by conduction• Simulation is time dependent
Hence the paraffin wax’s thermal properties had to be designed as a series of sensible heating stages.
Cs = 3412J/kgK for T<328K
Csl = 98587J/kgK for 328K<T<330K
Cl = 4466J/kgK for T>330K
Boundary conditions:• Mass flow rate of heat transfer medium 0.108kg/s at 333.2K• Fluid outlet subject to normal environmental conditions (293.2K and 101325Pa)
Initial conditions:• Same as normal environmental conditions
Results (for a model scale device):
• Thermal heat capacity – 381.7kJ
TESTING OF 1/5th SCALE PROTOTYPE
“CHARGING” of Device: “DISCHARGING” of Device:
Heat supplied thermal store = 595.8kJ
η = 64.1%
Heat retrieved from thermal store = 247.0kJ
η = 64.7%Overall efficiency =
41.5%
The device is primarily designed to be integrated with a central domestic heating system.
DEVICE INTEGRATION
The main heat sources for the device are:• Micro – CHP (automotive vehicle engines)• Surplus solar thermal heat
APPLICATIONS FOR THE DEVICE
Micro-CHP Solar
• Requires a portable heat transfer medium•Integration with an automotive vehicle
• Stationary application• Integration with the domestic central heating systemTwo primary heat sources:
• Exhaust gas• Engine cooling process
Yu, C., & Chau, K.T. (2009) Review on thermal energy storage with phase change. Renewable and Sustainable Energy Reviews, 13, 318 – 345.
Retrieved from duaemanus.blogspot.com
OVERVIEW OF A MICRO-CHP INTEGRATED DEVICE
Increase mass implies:
• a larger CAPEX• greater operating costs
• enhanced revenue
Scenarios
Displacement of gas heating
Displacement of electricity heating
• Main application for device is in micro-CHP
• Economically device is currently not very feasible for displacing the heating load from a gas boiler
• Optimisation of the design (improving PCM to total device mass ratio)
• Simulation testing for practical maximum efficiency
• Consequent optimisation of the practical model
• Further development of device fittings is crucial to the installation of the device
CONCLUSION
THANK YOU
ANY QUESTIONS?