As mentioned in Chapter 2, measurements that have been reported so far all involved oil lubricants for compressor. Also, due to the limitation of the conventional compressor, the refrigerant performance are compared at fixed condenser temperatures and pressure ratios but with different compressor conditions. The oil-free linear compressor can achieve compressor stroke control by changing power input. The oil-free operation also benefits the refrigerationsystem from preventing the blockage of the tube especially for small diameter heat exchangers and heat transfer deterioration due to oil lubricant. This chapter compares the performance of R1234yf with R134a based on the novel ORS introduced in Chapter 3 over a wide range of operating conditions. The elimination of oil lubricant enables comparable test conditions for better evaluating the performance of R1234yf and R134a and provides a potential for the ORS system using microchannel heat exchangers in the future. R152a experiments were also conducted at the same refrigerant charge. However, the ORS was overcharged using R152a due to its low vapour density. R152a is not included in the comparison of the system performance of the ORS.
example the water level over the blocks correctly simulated and the undular shape of the flow, and location of the rollers clearly identified. Furthermore, the location of the hydraulic jump after the obstructions is correctly predicted in terms of position, shape and height. A similar good result is observed for Trial 7, where for the lower discharge rate, there is both observed and simulated a reduction in flow over the side blocks compared with the high discharge case (figure 5c and 5d). Water levels are observed to be comparable and both the breaking wave that forms between the blocks and the shape and location of hydraulic jump are correct in the simulations. A similar level of good qualitative agreement for the free-surface location is also observed for Trials 5 and 6. Figure 6a shows the predicted free-surface location on a vertical plane down the centre of the channel for each of Trials 5-8. Figure 6b shows the same predictions in the region around the obstacles, at the same location, overlaid with the TLS measurements of the white-water surface. From this comparison it can be observed that although the main flow features are predicted well (for example the water levels, the slope of the water surface) the location of other features appears to be predicted too early along this central plane (for example the position of the wave undulation in Trail 6). However, it should be noted that these flows have a small degree of localised transient behaviour. This is observed both in the transient CFD runs and physical observations. As such, the CFD, TLS and photographic result are each a ‘snap-shot’ that are not exactly synchronised. This in part could be a cause of some small localised differences between the model and measurements. This will be investigated in more detail in the next steps of the work.
This work shows that a three-dimensional transient two-phase RANS CFD-VOF model can be used to predict the position of waves and hydraulic jumps within a complex hydraulic flow environment as measured during a series of full-scale experiments. A novel application of LIDAR is used to provide detailed measurements of the position of the water free-surface location during the physical experiments. The test environment is a recreational white-water course that provides a means to vary the flow rates of water and restrict the flow easily as required. Obstructions are added to the channel to create hydraulic jumps and other specific flow features. The influence of these obstructions on the flow has been analysed for size, velocity and position. The results of the study demonstrate that, although computationally intensive, the free-surface CFD approach can reliably predict a range of complex hydraulic flow features in medium/large- scale open channel flow conditions. In order to reliably capture the full three-dimensional characteristics of the water free-surface a high resolution mesh (greater than 2.5 million cells) with time-steps in the order of milliseconds is necessary (Simulations presented here represent between 30 and 60 seconds of real-time). Keywords: CFD, modelling, VOF, free-surface, hydraulic jump, white-water, LIDAR, TLS, waves, kayaking
To evaluate the performance of the proposed method under different conditions, we evaluate the algorithm with different width of the ellipse λ and possible region thresh- old l. The weighting parameter plays an important role in generating accurate RTI images. If the ellipse is too wide, the pixels of where attenuation is not occurring may be included. If the ellipse is too narrow, pixels that do, in fact, attenuate a link’s signal may not be captured by the model. This may result in a loss of information that degrades the final reconstruction quality. Figure 10a illustrates the mean squared error (MSE) with respect to different λ. It is obvious that the CMMS algorithm can achieve better results when λ in the neighborhood of the point 0.03. And the MSE with respect to different possi- ble region threshold l is indicated in Figure 10b. We can see that the MSE is very large (over 1.8 m) when l = 0.5 m, because the target may move out of the possible region which only comprises 5 pixels. The MSE does not signifi- cantly increase with the threshold l increasing, but a very large value of l will increase both the computational com- plexity and the system latency. Essentially, the threshold l is determined by V max and t int (l ≥ V max × t int ). If the
The NERMS, air sampling measurements, sampling of ground, water and vegetables samples and In- situ measurements provides the operational quantities for OIL recalculations in case of emergency. By the above measurements and data a more precise and specific optimization analysis can be carried out on the basis of actual data efficiency of protective measures. This should result in a specific intervention level for each protective measure, to be used as criteria in the medium and long term. Choosing lower or higher levels of intervention would mean allocating more or less efforts and resources in radiation protection.
With condensing technology, not only is the heat from the combustion of fuel oil or gas utilised, but also the heat that, with non-condensing heating technology, would otherwise escape unused up the chimney. Condensing boilers extract almost all of the heat contained in the ﬂue gases and convert it into additional heating energy. To do this, Viessmann condensing boilers are equipped with stainless steel Inox-Radial heat exchangers, which cool the ﬂue gases before they are routed into the stack, to the extent that the water vapour contained within them is deliberately condensed, transferring the additional heat released into the heating system.
building energy consumption analysis software DOE-2 and BLAST advantage, while the development of many new features, which uses the integrated load - Equipment - system synchronization simulation method, easy maintenance Fortran90 modular development structure, and in some functional connection with other software such as SPARK and TRNSYS. EnergyPlus HVAC system simulation can be achieved, including cold and heat source side equipment such as absorpt chillers, electric refrigerator, gas turbine chillers, boilers, cooling towers and other equipment as well as the end of the side fan coil units, VAV air box, and induction blower and so on. These devices were used in cold water, hot water and cooling water circuits connected together. Device simulation using the performance curve fitting, to add other types of modules  according to their needs. However, the current performance of the inverter multi air conditioning in the EnergyPlus simulation has not yet been achieved. Although domestic scholars also began to do some simulation of inverter multi air conditioning, its main purpose is to create a system of thermokinetic model to analyze the multi-linked system performance characteristics and test control algorithms. Combination of building energy consumption, and inverter multi air conditioning simulation studies have not been seen in the literature.
it blocks UV radiation from the sun. Highly energetic UV radiation called UV-C (wavelength 280 nm) is absorbed by the ozone molecules. UV-B radiation (wavelength 280 – 325 nm) is also absorbed. The ozone layer acts as a shield for us from very harmful UV rays. Exposure to UV rays causes skin cancer, damages crops, affects cellular DNA, impairs photosynthesis and harms ocean life. Observed and projected decreases in ozone have generated worldwide concern leading to adoption of the Montreal Protocol that bans the production of CFCs, halons and other ozone-depleting chemicals such as carbon tetrachloride and trichloroethane. R&AC has a vast scope. But the conventional technology using the heat carrying fluids viz. refrigerants (CFCs and HCFCs) renders it unsafe and very harmful. So on the basis of Peltier module Thermoelectric Refrigerator is used for cooling and refrigeration. Thermoelectric cooling  technology proves to be a promising
The vapour-compression refrigeration uses a liquid refrigerant as the medium which while circulating in the machine absorbs and removes heat from the space to be cooled and then rejects that heat into atmosphere. This system has four main components: a compressor, a condenser, a thermal expansion valve known as throttle valve or metering device, and an evaporator.
Abstract - The climate of the India comprises wide range of the weather across a vast geographic scale which can affect the coefficient performance of the solar adsorption refrigerationsystem. This paper primarily focuses on the performance and analysis of the solar adsorption system for tropical wet and dry climatic zone of India. The objective of this review is to understand the different parameters which may affect the solar adsorption refrigerationsystem .For that we have to consider certain factors which are relevant to the intensity of solar radiation such as local latitude, angle of inclination of the receiving surface, weather conditions etc. The system proposed consist of a glass tube having sorption bed, condenser and an evaporator. The working pair of fluid used is low grade charcoal and methanol .For the successful operation of this system the factors such as adsorbent-adsorbate pair, system design and arrangement of the subsystems have been chosen with great care.
readily available, not poisonous in any common concentration, and non-flammable. Currently it is not an easy matter for decision makers in commercial refrigeration to make a definitive choice when it comes to refrigerants and system type. For the last decade, many refrigerant options and system architectures have appeared both on paper and in practice. The sector has been in the environmental spotlight in recent years, especially as the leakage studies have revealed the true effects of HFC emissions in centralized systems. Considerable reductions in emissions are certainly possible, but they do require changes.
with the pair silica gel/water. This refrigerator is characterized by its compactness and its ability to be transported. The working volume of this refrigerator is 100 liters, the surface of the solar collector is 1m2 and its mass reaches 150 kg. This machine was built with materials to minimize the mass of the system. For better insulation of refrigeration compartment, vacuum panels (VIPs) were used, while a large storage volume capacity was maintained. An independent valve was developed to eliminate any human manipulation. Abu-Hamdeh  investigated some work on solar adsorption refrigerator using parabolic trough collector and uses olive waste as adsorbent with methanol as adsorbate. The author showed, from the COP values, that the optimal adsorbent mass varied between 30 and 40 kg while the optimum tank volume varied between 0.2 and 0.3 m3. Wang  developed a novel two-stage adsorption freezing machine, which is powered by the heat source with the temperature below 100°C. The composite adsorbents of CaCl2 and BaCl2 developed by the matrix of expanded natural graphite were chosen as adsorbents. The experimental results showed that the optimal coefficient of performance (COP) and specific cooling power (SCP) at 15 °C refrigeration are 0.127 and 100W.kg-1, respectively. COP and SCP increased with the increasing heat source temperature and decreased with the decreasing evaporating temperature.
The primary and secondary streams combine within the mixing section. The kinetic energy of this combined stream is transformed into pressure energy in the diffuser section of the ejector from where the combined vapor stream is fed to the condenser [Eames et al (1995b)]. The heat of condensation is rejected to the environment via the condenser and part of the resulting condensate is fed back to the generator via feed- pump whilst the remainder is expanded, via a throttling valve, to the evaporator where it absorbs heat at low temperature, causing it to vaporise and produce the desired refrigeration effect.
impossible to construct a device which, operating in a cycle, will produce no affect other than the transfer of heat from a cooler to a hotter body. The construction of vapor compression refrigerationsystem is illustrated in fig. 2. This system consists of four basic components, i.e. a compressor, an evaporator, a condenser and capillary tubes. Here the compressor delivery head, discharge line, condenser and liquid line form the high pressure side of the system. The expansion line, evaporator, suction line and compressor suction head form the low pressure side of the system. A drier is also installed in the liquid line which contains silica gel and absorbs traces of moisture presented in the liquid refrigerants so that it does not enter the narrow cross section of the expansion device causing moisture chocking by freezing.
regarding the use of conventional refrigeration technologies as they contribute to ozone layer depletion and global warming. Refrigerators that contain CFCs, HCFCs or HFCs in their refrigerant cycle or insulation foam are very harmful. All these are environmentally destructive and potential global warming chemicals. Also, there is an energy concern regarding the use of commercially available refrigerators. The commercial systems operate in a vapor compression cycle, in which a compressor does the major work of compressing the refrigerant liquid for cooling. As the refrigerators are usually operated for 24 hours a day, there is considerable energy consumption. The use of solar energy to power refrigeration with replacing the compression cycle with vapour absorption cycle strives to minimize the negative impacts refrigerators have on the environment and energy. Replacing the electrical energy with solar energy will reduce the consumption of high grade electrical energy. Also the replacement of compression system with absorption system eliminates the energy consumption by compressors. Ammonia being an environmentally friendly gas reduces the effect of ozone layer depletion and global warming by artificial refrigerants. This paper deals with a model solar refrigerationsystem using NH3-H2O vapour absorption system.
The intelligent method supporting the whole process of refrigeration engineering design is raised. Based on the technology of equipment selection and CBR, most repetitive works can be avoided. The intelligent design system is developed based on the actual demand of one famous domestic refrigerating enterprise. It is run on the general graphic platform AutoCAD, easy for enterprises to reuse design knowledge. The system can simplify the design process of refrigeration engineering enormously and reduce the design lifecycle. The principle, mechanism and structures of refrigeration engineering intelligent design system are also suitable for the other engineering products suit. As long as changing the product model and the design resource in the system design platform and developing corresponding user interface, it can be applied to the other product auxiliary design.
The idea of using sound wave for cooling gained interest in the 1960s. Even though the physical explanation of this refrigeration technique is simple, analysis of the phenomenon and the equations that describe it are not simple. The discovery of the thermo acoustic phenomenon goes back to more than a century ago; however, the significant work in this area was started about two decades ago at the Los Alamos National Laboratory. They have developed different types of thermo acoustic refrigerators and heat engines. A few other research groups are also working in this area. However, the development of such devices is still at preliminary stages. Garret et al. developed a new space craft cryocooler, which uses resonance high-amplitude sound waves in inert gases to pump heat, which was used in the space shuttle discovery. Tijani et al. achieved temperature as low as -65 degree Celsius in their thermo acoustic devices. They used it to study the effect of some important thermo acoustic parameters, such as the prandtl number by using binary gas mixture. Bailliet et al. measured the acoustic power flow in the resonator of a thermo acoustic refrigerator by using Laser Doppler Anemometry (L.D.A) together with microphone acoustic pressure measurement. They found good agreement between the experimental and theoretical results. Jin et al. studied thermo acoustic phenomenon in a pulse tube refrigerator. They studied the characteristics of the thermo acoustic prime mover and the effects of working fluid. They achieved a cryogenic temperature of 120 K in their experiments. Symko et al. used thermo acoustic refrigerator and prime mover to remove heat from an electronic circuit. They drove the thermo acoustic devices at frequencies between 4-24 kHz and investigated the performance of the devices. Jebali et al. analyzed
Whilst it is difficult to argue that liquid cryogens have no place in a terrestrial laboratory, they have serious drawbacks for use in space. Their primary shortcoming is the finite duration o f their cooling power. In order for them to provide cooling, liquid cryogens must necessarily be in contact with objects at temperatures above the cryogens’ boiling points. This means that gas will inevitably be boiled o ff and lost from the system. The rate o f the boil-off will depend on the amount o f cooling required, but for most space missions, lifetimes o f greater than 5 years would require prohibitively massive cryostats to be launched. As noted in Section 18.104.22.168.1 above, the feasibility o f replenishing cryogen stocks by means o f an in-orbit transfer has been demonstrated by the SHOOT mission. Nevertheless, the inconvenience and risks involved with such procedures makes the proposition o f a cooling system which could operate indefinitely without servicing seem much more attractive.
Abstract: The sun is an outstanding energy source for mankind. It is clean and comes to the earth for free. There is no need to drill and refine it or mine it out of the ground. The devices needed to gather its energy are simple, quiet and non-polluting. International environment protection initiatives have led to the intensification of research efforts on development of ozone and global warming safe refrigeration technology. In recent years, increasing attention is being given to the use of waste heat and solar energy in energizing refrigerating systems. Solar powered refrigeration and air conditioning have been very attractive during the last twenty years, since the availability of sunshine and the need for refrigeration both reach maximum levels in the same season. The adsorption refrigeration is based on the evaporation and condensation of a refrigerant combined with adsorption. The paper describes the design and fabrication of the experimental chamber, the experimental procedure and its feasibility towards development of an alternative eco friendly refrigeration cycle for replacement of chlorofluorocarbons. The objective of this paper is to establish an alternative eco-friendly refrigeration cycle for producing a temperature usually encountered in a conventional refrigerator. By manufacturing such type of refrigerator adds new dimension to the world of refrigeration. This refrigerator gives some amount of relief to the refrigeration world by making it independent of electric power supply and zero running cost.
ABSTRACT: The paper describes efficient method to develop a portable thermoelectric refrigerationsystem for medical application using thermoelectric cooling effect. Thermoelectric modules are the key elements in this refrigerator for providing the thermoelectric cooling. The one side of the thermoelectric module gets cooled and provide refrigerating effect while the other side becomes hot and rejects the heat to the environment with the help of fans and fins. It will evidently reduce the burden on our ecological system by reducing the pollution caused by CFCs and other toxic components. The proposed work is validated using experimentation.