Second law efficiency analysis of air injection into inner tube of double tube heat exchanger

At present study, thermal performance of a double tube heat exchanger due to stream of air/water two phase flow through inner tube is experimentally studied. Air and hot water were mixed in a T-junction outside heat exchanger and then were followed into inner tube of heat exchanger. Told water flow rate was kept constant and was equal to 2 lit/min. For hot water flow rate, four different flow rates of 3, 4, 5 and 6 lit/min was considered. Also inlet temperature of cold and hot water streams were almost constant and were within range of 17–19 C and 48–50 C. Also, for air flow rate five different flow rates of 1, 2, 3, 4 and 5 lit/min were considered. Volume fraction was within the range of 0.14 and 0.62. Obtained results were analyzed based on several energetic and exergitic parameters including pressure drop, effectiveness, Number of Transfer Units, heat transfer coefficient, dimensionless exergy loss and Witte-Shamsundar efficiency factor. Results presented an increment of 33% and 38% in heat transfer coefficient and Number of Transfer Units, respectively. Maximum value of Witte-Shamsundar efficiency factor was found to be 0.973 and was related to Volume fraction of 0.57 and has occurred at counter flo

A quick review of the applications of artificial neural networks (ANN) in the modelling of thermal systems

Thermal systems play a main role in many industrial sectors. This study is an elucidation of the utilization of artificial neural networks (ANNs) in the modelling of thermal systems. The focus is on various heat transfer applications like steady and dynamic thermal problems, heat exchangers, gas-solid fluidized beds, and others. Solving problems related to thermal systems using a traditional or classical approach often results to near feasible solutions. As a result of the stochastic nature of datasets, using the classical models to advance exclusive designs from the experimental dataset is often a function of trial and error. Conventional correlations or fundamental equations will not proffer satisfactory solutions as they are in most cases suitable and applicable to the problems from where they are generated. A preferable option is the application of computational intelligence techniques focused on the artificial neural network model with different structures and configurations for effective analysis of the experimental dataset. The main aim of current study is to review research work related to artificial neural network techniques and the contemporary improvements in the use of these modelling techniques, its up-and-coming application in addressing variability of heat transfer problems. Published research works presented in this paper, show that problems solved using the ANN model with regression analysis produced good solutions. Limitations of the classical and computational intelligence models have been exposed and recommendations have been made which focused on creative algorithms and hybrid models for future modelling of thermal systems.http://www.etasr.com/index.php/ETASR/indexdm2022Mechanical and Aeronautical Engineerin

Review of solidification and melting performance of phase change materials in the presence of magnetic field, rotation, tilt angle, and vibration

Due to the poor thermal conductivity of phase change materials (PCMs), the operation of Latent heat thermal energy storage (LHTES) is restricted by the limited heat exchange rate between PCMs and heat sources or sinks. The current review discusses the effects of magnetic field, rotation, tilt angle, and vibration on the discharging and charging heat performance of PCMs and nano-enhanced PCMs (NEPCMs) which are encapsulated in various container geometries and orientations based on melting and solidification standpoints. From this review, it is concluded that the orientation and design of the heat exchanger has a significant effect on the melting/solidification performance. The melting and solidification performance have been improved by increasing the magnetic number and decreasing the Hartmann number. Moreover, rotating cavity in a counter direction of buoyancy flow has improved the melting rate/time. The optimum tilting angle varies depending on the thickness of PCM layers. In terms of the vibration effect, frequency and amplitude/frequency are found to have an important role at low and high discharge rates, respectively. Following a comprehensive review, a few suggestions are provided as future research topic in this field

A Review of the Configurations, Capabilities, and Cutting-Edge Options for Multistage Solar Stills in Water Desalination

The desalination of saltwater is a viable option to produce freshwater. All the desalination processes are energy-intensive and can be carried out on a large scale. Therefore, producing freshwater using renewable energy sources is the most desirable option considering the current energy crisis and the effect that fossil-fuel-based energy has on our carbon footprint. In this respect, the tray-type still, one of several solar power desalination still varieties, is popular owing to its straightforward design, economic materials of construction, and minimal maintenance requirements, especially in isolated island regions with restricted energy and natural water supplies. The traditional tray-type solar power has a few drawbacks, such as the inability to recover latent heat from condensation, reduced thermal convection, a large heat capacity, and comparatively minimal driving power through evaporation. Therefore, the improvement of heat and mass transfer capabilities in tray-type stills has been the subject of many studies. However, there is a lack of a comprehensive review in the open literature that covers the design and operational details of multistage solar stills. The purpose of this paper is to present a thorough overview of the past research on multistage solar stills, in terms of configurations, capabilities, and cutting-edge options. In comparison to a unit without a salt-blocking formation, the review indicates that a multistage distillation unit may run continuously at high radiation and generate pure water that is around 1.7 times higher than a unit without a salt-blocking formation. The most effective deign is found to be “V”-shaped solar still trays that attach to four-stage stills, since they are less expensive and more economical than the “floor” (Λ-shape) design, which requires two collectors. Additionally, it can be stated that the unit thermal efficiency, solar percentage, and collected solar energy (over the course of a year) increase by 23%, 18%, and 24%, respectively, when the solar collectors are increased by 26% (at the constant inflow velocity of the water)