Abstract
M.Eng.
The need and problem was originated from the trends of the earths dwindling
energy resource. As time progresses humans are becoming more aware of
need to use so called “alternative energy sources” to alleviate the main
energy converters i.e. power stations. The student was tasked with
investigating the thermal performance of a solar powered refrigeration cycle
(prototype) that could:
produce enough refrigeration effect that it replaces the standard
home vapour compression unit, used for cooling or freezing of foods,
heats up a geyser sufficiently to have hot water for a common house
hold,
has excess energy to heat or cool liquid or air based environments
and
has the potential to lower the electrical bill of a house.
The introductory step was to obtain the thermo fluid properties of aqua
ammonia solutions. A setback came about when determining the aqua
ammonia properties. There were too many conflicting properties being
yielded by six different authors. In an attempt to gain confidence in only one
author a comparison table was prepared. The table compared the six authors
to each other. By looking at all the values compared it brought great clarity to
the problem. When continuing the research into the fundamental law
approach of solving for the cycle new findings were made. Initially very little
comprehensive studies were done which explained in fundamental laws to
solve for the absorption cycle. After extensive reviewing of a detailed study
on how to solve for absorption refrigeration cycles, then it was able to begin
improving on the thermo – fluid design of the cycle. As cycle and component
design began to progress the train of thought began to steer in a direction.
Each component needed to be detail designed. The advantage of having
each component specifically catered for in the cycle design was that it would
increase the cycle efficiency. In this way it would ensure that during the
concept generation phase the functioning of each component was clear,
thereby enabling a clear understanding of how components would
compliment each other in a cycle. A mode of solving for the cycle was to
endeavour that all parameters could be calculated unambiguously, with the
aid of computerisation. Testing was carried out on a real life commercial
thermal siphoning machine in order to realistically understand how
absorption refrigeration works and gain experience.
At the end of the study the most important result is that the dissertation
research shows strong evidence that it will be possible to create a device
which can fulfil the four tasks listed above. Another result is a program which
is a refined cycle design of the pump absorption type refrigeration. The
program solves for points along the cycle. Lastly it was found that even
though EES was the simpler program to use for aqua ammonia solution
properties it was the only program which catered for sub cooling and super
heating.