UWE Bristol Engineering showcase 2015

Temperature (°C)
Temperature (°C)
Temperature (°C)
Henry Thompson
MEng Mechanical Engineering
Project Supervisor
Rachel Szadziewska
Incorporating Storage Heaters into Building Fabric
Figure 3 – Diagram showing wall design produced in AutoCAD Revit..
Computational Fluid Dynamic (CFD)
A transient CFD model was created to simulate the
air flow within a room. Figure 7 shows the geometry
used. Once this model was working correctly the
geometry was altered to simulate the wall case. This
geometry is shown in Figure 8.
Project summary
Currently modern storage heaters are the choice
heating system to go into new flats due to their safety
as well as their relatively low cost for electricity. The
thesis details a history into thermography ,an overview
into building techniques and regulations involved with
the construction of dwellings and successful design and
development of a 2-Dimensional mathematical model.
A timber frame wall panel was constructed as a test rig
in order to complete thermal analysis of normal storage
heater operation and compare this to the storage
heater operation when inside a wall. Finally a
Computational Fluid Dynamics model has been
designed and developed to accurately simulate how
placing a heater inside a wall affects the performance.
Figure 1 - Diagram showing position of thermocouples.
Internal Operation of the Storage Heater
To understand the internal operation a series of
thermocouples were placed inside of the heater
shown in Figure 1. Simultaneously a 2-D semiimplicit
mathematical model in order to simulate
the operation. An example of the equation is
shown below.
Wall Design
In order to incorporate the heater into the building
fabric a timber frame panel wall was designed and
constructed shown in Figure 3.
Figure 7 - Image showing geometry used for CFD heater
simulation.
Figure 9 - Image showing geometry used for wall
simulation.
Various data lines were plotted on CFD-Post in order
to compare the simulations. An Example of these
results is shown in Figure 9.
30.0
Comparison of How Temperature Varies Between Simulations After 180 Minutes
Project Objectives
The main aim of this project is to design and develop a
new innovative approach to heating solutions within a
dwelling in particular to investigate how incorporating a
storage heater into the building fabric affects the
performance and the heat output of the heater
compared to standard operation.
T 0 t+1 = θ T 0 t 1 − 2Fo x + Fo x 1
+ Fo x2
2
+ 1 − θ T 0 t 1 − 2Fo x + Fo x 1
+ Fo x2
2
t+1
t+1
∆t k 1 T 2 ∆t k
ρ
∆y 1 Cp 1 ∆y 1
1 + ρ 2Cp 2 ∆y
+
2 T 4
2
ρ
∆y 1 Cp 1 ∆y 1
T t+1 1 + T t+1 2
2
2 + ρ 2Cp 2 ∆y 2
2
2
3 +
∆t k
1 +
1
∆t k
ρ
∆y 1 Cp 1 ∆y 1
1 + ρ 2Cp 2 ∆y
+
2
2
ρ
∆y 1 Cp 1 ∆y 1
2
2
2 + ρ 2Cp 2 ∆y 2
2
2
k 1 T t t
2 − T 0
+ k 2 T t t
4 − T 0
∆y
T t t
1 ∆y 2
1 + T 3 + ∆t
ρ 1 Cp 1 ∆y 1
+ ρ 2Cp 2 ∆y 2
2
2
In order to validate the solution obtained from
mathematical model a series of graphs were
created in order to compare. An example is shown
in Figure 3 which demonstrates a strong
correlation
600
500
400
300
200
100
0
Comparison of Node 7 for Different Experiments and Semi-Implicit Model
0 200 400 600 800 1000 1200 1400
Time (minutes)
Experiment 1 Experiment 2 Semi-Implicit
Figure 2 – Graph showing comparison of thermocouple results for nodes seven.
Figure 4 - Image showing thermal camera experimental
setup.
Figure 5 - Image showing equipment setup for
Experiment 2.
Experimental Testing
To measure how the heater performance is
affected a FLIR E60 thermal imaging camera was
used. Two experiments were set up shown in
Figure 4 and Figure 5. Using the camera software
analysis tool an average temperature was attained
from the two experiments. Figure 6 shows both
experiments following the same trend with varying
magnitudes.
140
120
100
80
60
40
20
0
Comparison of Thermal Camera Results
0 200 400 600 800 1000 1200 1400
Time (minutes)
Experiment 1 Experiment 2
29.0
28.0
27.0
26.0
25.0
24.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Distance From Heater (metres)
Heater Simulation
Figure 9 – Graph showing CFD-post result comparison after 180 minutes.
Wall Simulation
The results indicate that on average, during
forced convection periods, a 4.3% drop in heat
occurs in the room. CFD results successfully
simulate the effect the heater exerts on air flow
in the room. These results demonstrate a
temperature difference on average of 1.3%. This
difference is acceptable, since in most dwellings
this percent change in temperature attains by
simply leaving the door open.
Project Conclusion
This thesis has outlined successful design, development
and testing of an innovative heating solution for a
dwelling. Thermocouple results indicate that internal
heater performance is unaffected by placement in the
wall and a comprehensive 2-D mathematical model
accurately represents the internal workings of the
heater. Furthermore a test rig that has been successfully
designed and constructed has enabled a direct
comparison with the heater when covered.
To conclude, the installation of a storage heater into the
building fabric is a viable option to heat all dwellings.
The in-wall heater may improve the aesthetics of
heating devices in a dwelling while also maximising
space. With development, a double-vented heater could
heat two rooms at once, reducing the number of heat
sources, which in turn will minimise investment and
maintenance cost for the homeowner.
Figure 6 – Graph showing comparison of thermal camera results.