Vapors

In the 21st century, concerns about finding environmentally friendly, cost-effective, and efficient refrigeration solutions have grown. Thermoacoustic refrigeration (TAR) offers a promising solution to these concerns. This paper conducts a comparative analysis of thermoacoustic and traditional refrigeration systems to determine their efficiency, cost-effectiveness, and environmental benefits, particularly for low-income communities. Traditional refrigeration systems are widely used but they rely on refrigerants. In contrast, TAR, an emerging technology, uses sound waves for cooling, providing an eco-friendly alternative. This analysis considers various factors, including energy consumption, initial and maintenance costs, and environmental impact. The findings suggest that while TAR has the potential for significant environmental benefits and long-term cost savings, traditional systems currently offer higher efficiency and lower upfront costs. For TAR to become a viable alternative, advancements in its efficiency, reliability, and cost reduction are necessary. If these improvements are achieved, TAR could provide an environmentally friendly solution for low-income communities.

SUMMARYFive modes of operation (absorption, emission, single reflectance, at-tenuated total reflectance, and photoacoustlc) of a Nico}et 7199 FourierTransform Infrared Spectrophotometer have been investigated in order to deter-mine which modes were most suitable for qualitative analysis of Jet fueldeposits. The absorption and emission modes were'found to be the most advan-tageous for investigation of the bulk and surface properties of acceleratedstorage/thermal deposits where relatively large quantities of deposit aregenerally available.The general effects of fuel type, stress temperature, stress time, typeof spiking agent, spiking agent concentration, fuel flow, and postdeposltlonaltreatment on the chemical nature of accelerated storage/thermal deposits werethen investigated by FTIR by systematically varying these parameters.A correlation of the infrared spectra and chemical structure of modelfuel storage/thermal deposits has been attempted.INTRODUCTIONJet fuels undergo chemica...

The thermal effects which affect the development of leading edge cavitation in an inducer were investigated experimentally using refrigerant R114. For different operating conditions, the evolution of the cavity length with the cavitation parameter was determined from visualizations. The tests were conducted up to two-phase breeding. The comparison of tests in R114 and in cold water allowed us to estimate the amplitude of the thermodynamic effect. The results show that the B-factor depends primarily upon the degree of development of cavitation but not significantly upon other parameters such as the inducer rotation speed or the fluid temperature, at least in the present domain of investigation. These trends are qualitatively in agreement with the classical entrainment theory. In addition, pressure fluctuations spectra were determined in order to detect the onset of cavitation instabilities and particularly of alternate blade cavitation and rotating cavitation. If the onset of alterna...

Solar assisted thermoacoustic cooling is with the recent advances in energy conversion efficiency an interesting alternative to sorption based technologies. Although thermoacoustic cooling is characterized with a slightly reduced COP, is has the advantage to require little to no maintenance and has zero global warming potential. To successfully use the technology to cool office buildings an optimally designed machine and a careful building integration is required. To assess the integrated performance of building, thermoacoustic cooler and heat rejection system, the authors propose to use building and system performance simulation tools. However, there are no component models readily available to model a thermoacoustic cooler within those environments. In this contribution the authors aim to determine the needed modelling complexity level for a component model of a thermoacoustic cooler. As the energy conversion efficiencies are sensitive to geometrical and operational parameter of t...

The thermal effects which affect the development of leading edge cavitation in an inducer were investigated experimentally using refrigerant R114. For different operating conditions, the evolution of the cavity length with the cavitation parameter was determined from visualizations. The tests were conducted up to two-phase breeding. The comparison of tests in R114 and in cold water allowed us to estimate the amplitude of the thermodynamic effect. The results show that the B-factor depends primarily upon the degree of development of cavitation but not significantly upon other parameters such as the inducer rotation speed or the fluid temperature, at least in the present domain of investigation. These trends are qualitatively in agreement with the classical entrainment theory. In addition, pressure fluctuations spectra were determined in order to detect the onset of cavitation instabilities and particularly of alternate blade cavitation and rotating cavitation. If the onset of alterna...

Various models and equations of water vapor sorption by hydrophilic polymers were considered. It was shown that these models often do not correspond to the sorption mechanism. These models can be mathematically adapted to the experimental isotherm regardless of the real sorption mechanism. Even when sorption occurs according to the same mechanism, various authors use different models and equations. This study is based on the volume absorption mechanism and the Van Krevelen method of group contributions. As a result, a universal physicochemical equation was proposed, which makes it possible to adequately describe the sorption isotherms of amorphous hydrophilic polymers knowing only the chemical formulas of repeating units of these polymers. To calculate the sorption isotherms for semicrystalline samples, it is necessary to use an additional parameter, namely the degree of amorphicity (Y). The adequacy of the derived equation was verified for samples of cellulose and other natural pol...

The main motivation of conducting this work is to present a rigorous analysis and investigation of the potential effect of the heat pipe adiabatic region on the flow and heat transfer performance of a heat pipe under varying evaporator and condenser conditions. A two-dimensional steady-state model for a cylindrical heat pipe coupling, for both regions, is presented, where the flow of the fluid in the porous structure is described by Darcy–Brinkman–Forchheimer model which accounts for the boundary and inertial effects. The model is solved numerically by using the finite volumes method, and a fortran code was developed to solve the system of equations obtained. The results show that a phase change can occur in the adiabatic region due to temperature gradient created in the porous structure as the heat input increases and the heat pipe boundary conditions change. A recirculation zone may be created at the condenser end section. The effect of the heat transfer rate on the vapor radial v...

The local distributions of void fraction, interfacial frequency, and velocity have been measured in annular flow of R-134a through a wall-heated, high aspect ratio duct. High aspect ratio ducts provide superior optical access to tubes or irregular geometries. This work expands upon earlier experiments conducted with adiabatic flows in the same test section. Use of thin, transparent heater films on quartz windows provided sufficient electrical power capacity to produce the full range of two-phase conditions of interest. With wall vapor generation, the system pressure was varied from 0.9 to 2.4 MPa, thus allowing the investigation of flows with liquid-to-vapor density ratios covering the range of about 7 to 27, far less than studied in air-water and similar systems. There is evidence that for a given cross-sectional average void fraction, the local phase distributions can be different depending on whether the vapor phase is generated at the wall, or upstream of the test section inlet....

Thermoacoustic Refrigerators use acoustic power for generating cold temperatures. The development of refrigerators based on thermoacoustic technology is a revolutionary answer to today's cooling needs that does not harm the environment. These devices can achieve very low temperatures while keeping a compact size, thanks to features such as limited moving components and the lack of CFC refrigerants. In this work experimental study has been performed on Thermoacoustic refrigeration system by using air as the working fluid. Focus of the present investigation is to see the effect of changing design and operating parameter on temperature gradient across the stack. Here the stack position has chosen as design parameter whereas for operating parameter frequency has been selected. The results obtained from the experiments have been discussed in result and discussion section of this report. The analysis shows that operating nearer to optimum designed frequency offers better results while stack position of 100mm offers comparatively better results when stack is at 50mm.

In the last years, experimental diagnosis and therapy for cancer patients is performed using nano-micro technologies, and in particular iron nano-microparticles since their ad/absorbance properties, are useful in transporting and maintaining drugs in tumor regions. In this paper, a plasma generation process is used for spraying solid metal (carbon steel wire or rod). By modifying the electric current intensity, material�s displacement speed in plasma and the debit of technical argon, iron nano-microparticles are obtained in the form of filled and/or porous microspheres, nano-microtubes and microparticles. They consist of a central core from which tentacles in the form of microtubes emerge. We show the manufacturing process and the formation mechanisms of these particles by using argon plasma. We present and discuss the obtained results.

Vortex cavitation in a submerged transitional jet is studied with unsteady three-dimensional direct numerical simulations. A locally homogeneous cavitation model that accounts for non-linear bubble dynamics and bubble/bubble interactions within spherical bubble clusters is employed. The velocity, vorticity, and pressure fields are compared for both cavitating and noncavitating jets. It is found that cavitation occurs in the cores of the primary vortical structures, distorting and breaking up the vortex ring into several sections. The velocity and transverse vorticity in the cavitating regions are intensified due to vapor formation, while the streamwise vorticity is weakened. An analysis of the vorticity transport equation reveals the influence of cavitation on the relative importance of the vortex stretching, baroclinic torque, and dilatation terms. Statistical analysis shows that cavitation suppresses jet growth and decreases velocity fluctuations within the vaporous regions of the...

Due to the increase in energy prices and spiralling consumption, there is a need to greatly reduce the cost of electricity within data centers, where it makes up to 50% of the total cost of the IT infrastructure. A technological solution to this is using on-chip cooling with a single-phase or evaporating liquid to replace energy intensive air-cooling. The energy carried away by the liquid or vapor can also potentially be used in district heating, as an example. Thus, the important issue here is “what is the most energy efficient heat removal process?” As an answer, this paper presents a direct comparison of single-phase water, a 50% water–ethylene glycol mixture and several two-phase refrigerants, including the new fourth generation refrigerants HFO1234yf and HFO1234ze. Two-phase cooling using HFC134a had an average junction temperature from 9 to 15 °C lower than for single-phase cooling, while the required pumping power for the central processing unit cooling element for single-pha...