University College Dublin
School of Electrical, Electronic and Mechanical Engineering
Application of Heat-Transfer Nanofluids in Ground Source Heat Pumps
Roohollah Ebrahimi, Kenneth T. Stanton
UCD School of Mechanical & Martials Engineering, Belfield, Dublin 4, Ireland
Project Summary
Nanofluids (fluids containing nanoparticles) influence several properties of the base liquids. Specific heat capacity, conductivity, density and
viscosity are some main characteristics of every fluid that change depending on the amount of nanoparticles dispersed in the base liquid.
By considering the issues facing the world in energy crisis which results in higher electricity rates each year, applying novel cooling and
heating systems especially for countries without mineral resources, seems to be unavoidable. An area of high interest in low energy
heating-cooling systems is ground source heat pumps (GSHP). The main benefit in this system is the utilization of the infinite capacity of
the ground which alleviates the amount of work needed for the heat transfer. The expanding usage of this GSHP as shown in Figure 2
shows the high demand for oil-independent energy systems.
We have set up a study to investigate the possibility of the use of nanofluids in ground source heat pumps coupled with under floor
heating-cooling in order to improve its efficiency resulting in an less electrical usage.
This project aims to introduce the most effective nanofluid which has been proven to have the highest heat transfer characteristics,
theoretically and experimentally. A minimum target of 4% energy saving has been estimated.
Renewable captured energy equals 2
Mtoe (Mega tons of oil equivalent) [3]
which is worth 1.5 b$ per annum
a
b
MWth
Total units
Figure 1. Benefits of nanofluids compared to microfluids (a) and an image of Fe2O3 nanofluid [1]
Model
Properties of nanofluids
Figure 1. Thermal energy captured and the No. of GSHPs installed in Europe by 2010 [2]
Solution
Issues with nanofluids
- Increase in viscosity which leads in higher pumping power
- Decrease in heat capacity which leads to lower heat transfer
Figure 3. Volumetric heat capacity of nanofluids compared to base fluid based on Matlab code
Results
As outlined above, the downside of nanofluids in heat transfer is the
heat capacity. Various calculations have been made to investigate the
effect of nanoparticles on the heat capacity. Calculations have shown
that a nanofluid made by nickel nanoparticles with a good
approximation do not affect the heat capacity of the base fluid
(water). With this approach, thermal properties are entirely increased
and the optimum point will only depend on viscosity.
In order to measure the enhancement of the chosen nanofluid an
experimental rig (Figure 4) is especially built for this purpose
Conclusion
Figure 4. 3D model of the experimental rig designed and built in fluid mechanic lab
By replacing the chosen nanofluid in GSHPs and achieving the 4% energy reduction, some 60 m$ could be saved per annum. The
mathematical calculations have narrowed the wide rage of nanoparticles to a specific material (Ni). Moreover, with the precise experimental
rig, the next step which the experimental tests will be achievable.
References
[1] J.A. Eastman, Fluctuations and Noise in Out of Equilibrium Systems, Sep 14-16, 2005
[2] Heat pump barometer - EUROBSERV’ER – September 2011