Advances in Air Conditioning and Refrigeration

Solar technologies like flat plate solar collectors are being widely used for low-grade thermal energy for household purposes. These days, photovoltaic thermal (PV/T) collectors are also gaining momentum as source of combined heat and electric power. Commonly used base fluid in PV/T collector is water which have low thermal conductance, and thus, addition of nanoparticles in base fluid will lead to the enhancement in overall thermal conductance. Keeping this as main focus, a research has been carried out to evaluate the performance of PV/T system with different nanoparticles. For that, the simulation was carried out by performing grid test and then simulated on ANSYS to obtain results. For the same, nanofluids with 20 nm particle dimensions and 299 K inlet temperature were loaded with 0.5, 1 and 1.5% particle volume fraction with different Reynolds numbers varying from 250 to 1500. The simulated model was validated with the literature, and obtained results showed that the heat transfer coefficient (HTC) without any nanoparticles ranges from 245.5 to 519.8 W/m2 K for Reynolds number of 250–1500, respectively. On other hand, with nanoparticles, the HTC increases and ranges between 250.6–529.20 W/m2 K, 255.42–539.8 W/m2 K and 261.1–550.8 W/m2 K for 0.5%, 1.0% and 1.5% volume fraction, respectively, for Reynolds number of 250–1500. In the end, it is concluded that the simulation results are in good agreement with the literature.

Unlike industrially developed economies, weaker societies lack infrastructure for transportation and storage of agricultural produce. This leads to demand for many small cold store facilities distributed widely, instead of a few large and energy-efficient units. Solar energy gives a clean and environment-friendly option for meeting this need; but solar energy is available only for about a third of the day, leaving a challenge to save applications needing round the clock air conditioning. Recently (2015), a new technology has been proposed by Al-Ugla et al. [1] of Saudi Arabia to circumvent the problem by employing a modified vapour absorption refrigeration cycle. The authors have shown on the basis of theoretical modelling that it is feasible to design and build a modified vapour absorption refrigerator that will provide 24 h cooling without storing the refrigerating effect below room temperature. The proposed system is expected to be compact in volume and economical to operate. We are on the path of developing a practical cold store to store about 5 tonnes potato or equivalent quantity of other produce in rural setting at moderately low temperature. The system is based on the classical LiBr/H2O absorption refrigeration cycle, the heat supply being given by solar power. Night operation is implemented by providing extra storage tanks to save rich mixture, lean mixture and pure water when solar heat is no more available for generating the refrigerant from the rich mixture. A vapour absorption refrigeration process is similar to the more common vapour compression system except that the mechanical compressor of the latter is replaced by an absorption-pumping-desorption process to achieve the objective of increasing the density, and consequently the pressure of the refrigerant. A common chemical system consists of LiBr and H2O, the latter being the refrigerant and LiBr the absorbent, and the process is illustrated in Fig. 1. While the vapour absorption cycle is well established, particularly, for generating refrigerating effect using low-grade heat or solar radiation, the focus of our project is to create a system that saves potential refrigerating effect (not a cold fluid) for use during night hours. The innovation introduced by Al-Ugla et al. revolves around extending the duration of operation by adding three secondary storage tanks—one for the strong (more water) solution, one for the weak (more LiBr) solution and one for the pure refrigerant (water), connected in parallel with the respective primary containers. During the daylight hours, the normal vapour absorption process, running in solar heat, produces the required cooling effect and excess amount of poor (weak) solution and pure refrigerant (water) which is stored in separate tanks for later use. This system should be distinguished from competing refrigeration storage systems where cooling effect is stored for the night either in the form of excess chilled water or in the form of solidified phase change material. The latter materials are bulky and expensive. In contrast, the proposed system stores the strong and weak solutions in separate tanks, with very high effective cooling capacities. The resulting secondary tanks are small, light and inexpensive. The machine will operate with 70 °C as evaporator temperature and 90 °C as generator temperature. The solar collector size is around 24 m2 for 24 h run. The major challenge is to maintain vacuum inside the system. In summary, the system proposed, herein it is characterized by the following features. (a) No external supply of electricity (grid connection) not necessary, (b) 24-hour operation (including night hours). (c) Based on vapour absorption cycle using LiBr as absorbent and water as refrigerant. (d) No expensive refrigerant or phase change material involved, nor there is a need for a large reservoir for storing refrigeration effect. (e) Small solar PV unit (200 W) with battery to power the three magnet-linked liquid pumps. The system is under development in our HVAC laboratory. Theoretical design is ongoing and results will be presented in the conference. A cost comparison between the system under development and two competing conventional systems (grid connected and solar PV + Battery) will be presented.

Cryopreservation is the method of the preservation of biological tissue samples for future usages without incurring significant changes to functional properties. A two-dimensional numerical model is developed in the current work to study the role played by MgO nanoparticles in enhancing the freezing rate of the tissue during cryopreservation. The Pennes bio-heat model is the governing equation in this case. Finite volume method is employed to discretize the governing equation while the tri-diagonal matrix algorithm is used for solving the discretized algebraic equations for obtaining temperature distribution within the tissue. The movement of solid–liquid interface during freezing is tracked using the enthalpy-porosity method. Validation of this model is first done with the result of the existing literature. Then, the effect of MgO nanoparticles in enhancing the freezing rate is studied by increasing the volume fraction of the nanoparticles in the tissue-nanoparticle system up to 30%. Finally, a comparative study is made to analyse the performances of MgO and Fe3O4 nanoparticles in quickening the freezing process during cryopreservation.

Due to low critical temperature, the performance of a conventional, single-stage R744-based transcritical refrigeration cycle drops drastically when the heat sink temperature is high. However, the performance can be enhanced by subcooling the refrigerant at the gas cooler exit. The present study is carried out to investigate the performance of an R744-based refrigeration cycle integrated with an R744-based auxiliary cycle to subcool the refrigerant at gas cooler exit. This modified cycle is termed as the cycle with dedicated mechanical subcooling (CDMS). This modified cycle is shown to give superior performance compared to the conventional cycle and cycle with internal heat exchanger. For this proposed cycle, the important operating parameters are optimized based on thermodynamic analysis. The results reported in this study are helpful in designing R744 transcritical refrigeration system integrated with auxiliary subcooling cycle.

Currently, the trough-type solar collector incorporated with storage unit is receiving significant attention because of their capacity to retain excess heat during non-availability of insolation. Thus, the objective of present study is to investigate the trough collector thermal performance which is built-in with storage container experimentally. The study is performed for south-facing and tracking modes of working in the end of November month. The performance is estimated in terms of collector thermal efficiency, gain in useful heat, storage tank water temperature rise, system overall and charging efficiency by fabricating and testing the simple structure of parabolic trough collector (PTC) system. Results show that PTC is capable to heat the water stored in the storage tank during both modes of working. The highest collector thermal efficiency is obtained as 54.4 and 53.04% during south-facing and tracking modes, respectively. The maximum system charging efficiency is found to be 87.98% in south-facing and 89.8% in tracking modes.

A numerical study is conducted to investigate the impact of mixture of refrigerant on the cooling performance of an inertance pulse tube refrigerator (IPTR). The influence of helium–hydrogen mixture on the cooling capacity is investigated numerically. Conservations of mass, momentum and energy equations are solved in the computational domain of an IPTR by finite volume method using FLUENT. Properties of helium–hydrogen mixture have been estimated by utilizing ideal gas law and are provided to the FLUENT as user-defined functions. It is seen that with an increase in the molar percentage of hydrogen than helium in a helium–hydrogen mixture, it enhances the cooling capacity, attains a maximum value and then decreases. It is examined that at a composition of about 50% hydrogen and 50% helium, the cooling capacity increases by about 11.51%, and further increase in hydrogen percentage than helium reduces the capacity.

To suffice the cryogenic cooling requirements for various academic and commercial applications, high refrigerating capacity GM cryocoolers have been used widely because of its compact size. Numerous innovative design approaches have been proposed and implemented to reduce the loss mechanisms to enhance its refrigeration capacity. In this paper, the structural and thermal effects of a cold-head cylinder are studied numerically. In place of a cylinder of constant diameter along the axial direction, three different types of stepped cylinder configurations have been used. Variations of von Mises stress, temperature, equivalent strain, maximum and minimum principal stress for different cylindrical configurations have been examined. It is seen that after reducing the cylinder thickness, total deformation along the radial direction of cylinder increases. Also, the von Mises stress increases, but its value is much lower than that of yield strength of SS-304. The results will be helpful for better design of cold-head cylinders for GM cryocooler from structural and thermal point of view to avoid structural failures.

The one-dimensional design methodology of radial turbine blade profile has a substantial role in the advancement of an efficient liquefaction cycle (cryogenic fluids) because of growing demand in research and various industrial applications. The main part of the current study is to obtain an optimum design of radial turboexpander. The CFD analysis of a turboexpander is carried out to characterize the flow filed inside it. The initial blade profile is generated using ANSYS Blade-Gen which is further modified based on CFD analysis. The pressure, temperature, velocity, static enthalpy and entropy at various cross sections are reported.

Solar energy is clean, renewable, abundant and free. The light and heat energy can be harnessed by using several technologies such as solar heating, photovoltaic cell and photosynthesis. Solar collectors are used for collecting solar thermal energy by heating and reheating a stream of water. This paper focuses on improving performance of solar flat plate collector using twisted tape. Flat plate collectors have a wide range of usage in industrial, public as well as residential sectors. Solar water heaters are environment-friendly, cheap to operate and need very little when compared with other solar applications. Many researchers are working to enhance the thermal efficiency of solar water heaters. The thermal efficiency enhancement can be done by modification of design of parts of solar flat plate collector such as absorber plate, STs, working fluid, thermal insulation, efficiency of fin and selective coating of an absorber plate. Use of twisted tape is an efficient method to increase the thermal efficiency by increasing the heat transfer by increasing the contact surface area between the water and metal tubes (inserted tape tubes) and also by promoting turbulence of flow.

Refrigeration system involved with evaporative heat transfer intends to intensify the cooling effect in domestic applications. In order to reduce the energy consumption and improve the cooling rate, various attempts have been undertaken. In this experiment, the exploitation of a refrigerating system using R-134a as refrigerant has been studied. The study also explains the thermal conductivity, dynamic viscosity and rate of heat transfer of graphene used as nano additives in evaporator tube of a vapour compression refrigeration (VCR) system. The thermal conductivity of base refrigerant rises with rise of temperature to the optimal concentration value of 0.6–0.9% by wt. in nano additives. In addition, significant improvement in the performance of refrigeration system due to the addition of nano additives in domestic refrigerant has been addressed. However, the apprehension of global warming due to potential use of R-134a as refrigerant is still a matter of concern. Hence, the paper encourages the use of nano refrigerant that leads to improvise the effectiveness, durability and energy efficiency of refrigeration without any system modification.

Flow behaviour of a capillary tube in the transcritical CO2 cycle is predicted based on homogeneous and separated two-phase flow models. Five different empirical correlations of void fraction available in open literature are used to predict the flow behaviour by separated two-phase model. Fauske [1] void fraction correlation matches reasonable well with homogeneous flow model with the discrepancy in capillary tube prediction as around 2%. It is observed that the homogeneous flow model is sufficient enough and recommended to predict the capillary tube flow in a transcritical CO2 system used for capillary tube modelling due to its simplicity and relatively lesser computations.

Transforming the salt brackish water into fresh water is a real global problem. To solve this problem, a simple and economical solution in the form of the solar distillation was used. Traditional methods of the solar distillation did not succeed, because the yield of the solar still is low. So a solution is suggested in the present work to increase the profitability of the fresh water. One of the best ways is to include materials for the storage of the thermal energy, i.e., the temperature elevation of a material allows for the storage of energy and that is exactly the purpose of the present work. An aluminum oxide nanoparticles were prepared, with dimensions which are in the range of 6 nm, and it was applied successfully for the first time in a single-slope solar still under outdoors of El Oued city (Southeast of Algeria) climatic conditions. Three solar basins exposed to the sun under the same weather conditions and each of them containing two liters of the salt water were utilized in the experiments. The first solar still is used as a reference for the purpose of the comparison and contains the water only. The second still contains in its basin (1 g/L Al2O3), while the third one contains in its basin (2 g/L Al2O3). The results of this simple and inexpensive technique were improved that the productivity of the (second and third) solar stills was increased, respectively, in high percentages (i.e., 127 and 174%). It can be concluded that the suggested technique can be used efficiently to solve the shortage of the fresh water problem in El Oued city (Southeast of Algeria) by mixing Al2O3 nanoparticles with the salt water inside the solar still.

The present work involves the investigations related to heat transfer between three fluids which are at three different temperatures. For investigation process, an innovative triple-concentric-pipe heat exchanger is adopted. The heat exchanger is designed in the laboratory. Normal tap water, water at an elevated temperature and water below the room temperature are chosen to be the three fluids of interest. N-H-C and C-H-N flow configurations are considered for the experimentation. Different flow configurations (with/without corrugation on the outer surface of the middle pipe) are also considered in the investigation. For the different flow arrangements, the temperature distribution pertaining to the different fluids is measured experimentally. This is presented separately for different flow arrangements. Effective heat transfer is calculated for each of the arrangements and compared. It is evident that heat exchanger effectiveness is better in case of corrugated surface and also the N-H-C arrangement of heat exchanger is seen to be more effective in comparison with the C-H-N arrangement.

Intumescent material is a type of material which can be regarded as one of the best types of thermal insulators for passive fire proofing as well as in thermal insulation in air conditioning industries. They can be used as a thermal barrier in various refrigeration and cooling systems. Such a material in refrigeration and cooling system will not allow the heat from the outer system to get conducted within it. This paper tries to justify the capability of the mixture having corn starch, baking soda and PVA glue as stated by NightHawkInLight through experimental setup to find its usage in refrigeration and air conditioning systems as a thermal insulator. The thermal conductivity and dielectric permittivity of the starlite material were found out. Furthermore, a flame test using oxyacetylene flame was conducted to check the maximum range of temperature that the material can sustain.

This paper has presented a comparative study of the positioning of an air conditioner in a room using computational fluid dynamics (CFD) simulations. Four different positions namely lower, middle, upper half of wall, and centre of the roof have been studied during this research work, and effect on different thermos-fluid characteristics has been evaluated for these positions. A comparative analysis of these effects has been presented. Considering the overall thermo-fluid flow performance, the current study suggests mounting position at the upper half of the wall as the most suitable among the positions considered.

The major problem for most developing countries is the shortage of good and clean drinking water. In the present experimental study, the conventional basin type has been modified to inclined pyramid single basin solar pond and produced distillate from the still. Tests were carried out for different water samples, namely saline water and mud water with a quantity of 750 g of salt in 10 L of freshwater and 10 L of mud water, respectively. To conduct the experiment, solar radiation has been checked by using a pyranometer. In order to enhance the distillate efficiency, the glass roof inclined angle was maintained as 61.9°. Both for desalination and mud water purification performances were observed. Both the experiments were conducted on inclined-type single basin solar pond set-up. The laboratory results showed that the pH values for desalination and mud water purification were 7.4 and 7.2, respectively. The total desalination and mud water purification efficiencies were found 15 and 16%, respectively, also the total solar radiation on glass cover was 6 kWh/m2/day and the average ambient temperature was 26 °C.

Superconducting magnets have traditionally been used in MRI medical diagnostic equipment, particle accelerators and a variety of industrial applications. Although most magnets made in our country so far have used low Tc superconductors operating at liquid helium temperatures, there is a distinct possibility that magnets of tomorrow will be made of high Tc materials that offer zero resistance around the temperature of liquid nitrogen (77 K). The optimum temperature for operating these magnets will be around 40–50 K, which is achievable by using GM-type cryocoolers. Unfortunately, in spite of nearly a century of experience in cryogenic technology, our country continues to import basic cryogenic cooling equipment. It is time for taking up indigenous development of such important and easy-to-achieve equipment. We are happy to report that such a development project has been taken up by the authors at the C. V. Raman College of Engineering, Bhubaneswar. The target of the development project is to design and build a GM-type closed-cycle cryocooler delivering about 100–150 W of refrigeration at 45 K. The paper presents the design methodology and means of construction. The complete design, fabrication and testing process are being documented so that other workers in India, both researchers and entrepreneurs, can build their own systems and even improve on our design, without additional help from any quarter. The objective of the present activity is to develop the complete end-to-end indigenous technology so that a techno-entrepreneur can initiate a business start-up basing on our experience and our recommendations..

In this study, a shell and coil tube heat exchanger used in a solar domestic hot water system is numerically studied. A 3-D model of the SCTHE is prepared using the commercial software package ANSYS 16.1. The result of the current approach is verified and validated with the results available in the literature with good conformity. Simulation runs are performed to determine the effect of three major parameters, i.e. the mass flow rate of the coil-side fluid, the mass flow rate of the outer annulus-side fluid and the inlet temperature of the coil-side fluid on the thermal performance of the SCTHE, i.e. overall heat transfer coefficient and heat transfer effectiveness. It is found out that with the increase in inner Dean number, outer Dean number and inlet temperature of the coil-side fluid, the overall heat transfer coefficient increases in every case; however, the effectiveness decreases with increment in inner Dean number and inlet temperature of the coil-side fluid and increases with increment in outer Dean number.

An exergetic investigation for heat transfer among different fluids in a combined three-fluid heat exchanger and solar flat plate collector system is carried out here. Present three-fluid heat exchanger (TFHE) is a modification of double pipe exchanger, where an additional helical coil is included between two concentric straight pipes for enhanced performance. The present study is an extension of previous published experimental work, where the effects of flow and thermodynamic parameter on exergetic characteristics of the TFHE are assessed in counter flow configuration. For this study, mass flow rate of different fluids and inlet temperature of hot fluid are chosen as the input parameters, whereas exergy loss and dimensionless exergy loss are considered as the performance parameters for this study. It is found out from the result that the exergetic performance of the TFHE is significantly affected by hot water and normal water mass flow rate. Inlet temperature of hot water is also other major contributing factor towards prediction of exergy loss in TFHE. It is noticed that exergy loss increases with rise in inlet temperature of hot water through helical coil in TFHE. Maximum exergy loss observed at higher mass flow rate and inlet temperature of hot water flow in TFHE.

A comparative analysis of cascade refrigeration system is presented in this paper. Different pairs of refrigerants are used in this simulation. Both energy and exergy analyses have been conducted. Since a cascade system uses two different refrigerants, R744 is used in the low-temperature unit and R134a, R717, R1234yf, R290, R1234ze, R600 are used alternatively in the high-temperature unit for the purpose of comparative study. Values of COP and the second law efficiency are evaluated and compared with each different pairs of refrigerants used. This paper shows whether the use of refrigerants with low ODP and GWP values is viable or not. The sole purpose of this paper serves in identifying an appropriate refrigerant pair with lower environmental risk which can be really efficient in operating a cascade system. It was observed that R744-R717 attained the highest COP value equivalent to 7.848, and the highest ECOP value of 0.9838 was also attained by R744-R717. R744-R600 also obtained COP value of 7.741 and ECOP value of 0.9833 which is quite good.

Domestic refrigerators typically use fin-and-tube type heat exchangers with variable fin pitch across the tube rows to accommodate for the reduction in the flow area due to frost formation. In the current study, a numerical model is developed in Modelica language to predict the heat and mass transfer across a typical tube–fin heat exchanger employed in a domestic refrigerator. Results obtained from the numerical model are validated using a purpose-built experimental setup. A comparison between the experimental and numerical results showed good agreement. Frost formation rate observed is constant, and the rate of heat transfer is higher in the bottom rows and decreases along the direction of the airflow.

The sun rays are concentrated through the parabolic disc mainly to the building roof, and the outside walls of the buildings exposed to the solar [1, 2] radiation are insulated as well as act as a heat storage unit with the use of PCMs and PCM mixed with metal slurry [3] mainly aluminum, steel, etc as thermal conductivity enhancer [4, 5] or heat transfer enhancer [6]. The paper mainly focuses on the total cycle of the PCM i.e. melting and solidification of the phase change materials. The numerical analysis for the melting cycle incorporates with complex transport phenomena. The mass, momentum and energy conservations equations are formed and numerically validated for the method from the experimental data. The Glauber salt-based heat storage devices contain high energy density and repeatability of usage over a period of time with chemical stability of the PCM. The experimental setup is made as well as numerical model validated through the heat exchanger unit by monitoring and collecting the continuous temperature over a prolonged period of time by using computerized data acquisition system. The rectangular fins [7] attached to the base plate of the aluminum are used as a thermal energy enhancer. The enthalpy update scheme-based 2D numerical model is used. TDMA solver is incorporated for solution. The paper indicates that the time for solidification of the system is studied with the melting pattern, temperature distribution and the stream function plots.

The change in climate and the depletion of the conventional energy storages pushes the thoughts of energy consumption as well as the energy efficient building and equipments in a large scale. The present work focuses on building energy assessment, optimization, recent advancement in energy-efficient building, etc. The different parameters affecting the building energy consumptions and how to minimize the use of energy by different methods are discussed. The case studies are needed for convincing both government agencies (responsible for ECBC [1] implementation) and builders and building design teams about the advantages of energy-efficient buildings. Monitoring of energy performance of buildings is a challenge due to non-installation or non-functioning energy information system (EIS) in majority of the buildings. The wide application of PCM-based material of different forms like encapsulation [2], slab and other forms like mixing with mortar and the wall and roof design applications are considered here.

Traditionally, vapour compression system used in vehicle air conditioning causes reduction in engine power and increases fuel consumption 15–20%. In internal combustion engine, only 30–35% of fuel energy is converted into useful work and about 50% energy of fuel is released as heat to the atmosphere. The exhaust from IC engine has waste heat in the temperature range of 150–400 °C. This exhaust heat of IC engine can be employed for the vapour absorption system which requires low-grade heat source. In this article, the energy and exergy analysis of vapour absorption cooling system powered by waste heat of IC engine exhaust is presented. The effect of absorber and generator temperatures on the COP and exergetic efficiency of vapour absorption cooling system is determined. The exergy destruction in components and performance parameters like COP, exergy efficiency are also computed. The aim of present article is thermodynamic evaluation of the utilization of exhaust heat of IC engine for vapour absorption cooling system heat by both first law and second law approach.

In this paper, studies on a commercial parabolic trough solar collector (PTSC) using supercritical CO2 (s-CO2) as the heat transfer fluid (HTF) are presented. When compared to other HTFs, supercritical CO2 can operate at higher temperatures which is useful for power plants. The collector module used for this study is LS-2 module. The effect of mass flow rate and inlet temperature of the HTF on receiver wall temperature, thermal loss, heat transfer coefficient and thermal efficiency is analysed. CO2 is taken in supercritical state in order to facilitate the direct integration of the collector to high-temperature power cycles. It is found that higher mass flow rate results in lower wall temperature and higher heat transfer coefficient. At any particular mass flow rate, lower operating pressure results in higher wall temperature. Rise in HTF inlet temperature results in an increase in wall temperature and reduction in thermal efficiency of the collector. However, variation in operating pressure results in negligible change in wall temperature.

For residential air conditioning applications, R410A has been used extensively. The global warming associated with the refrigerant is very high. This has led to further complications in the environment which was identified much later. Initiatives have been directed toward solving this dilemma. This research primarily focuses on creating binary and ternary refrigerant replacements for R410A. The conformability to the pressure–temperature characteristics, the increase in performance and the reduction in global warming potential was analyzed using computational methods. A MATLAB code was generated for the purpose of the calculation of the thermodynamic properties. The code was verified using REFPROP software. The accuracy of the code was very high. Four binary refrigerants and four ternary refrigerants were considered as replacements, and the results were obtained using the MATLAB code. One particular ternary refrigerant RT4 is resulted in a 34.938% reduction in the global warming potential while giving an increase of 4.335% in the performance of the refrigeration system.

Building envelope in houses is accountable for the enormous heat gain. This numerical study focuses on the influence of lightweight aggregate in the concrete for the heat gain in the building due to the sun’s radiation. Four lightweight aggregates, such as gravel, stalite, lytag, leca and argex were selected for inclusion in concrete and silica fume where it was added to the mortar. Transient thermal characteristics subjected to regular thermal excitation were solved using the admittance method through a computer simulation program. From the result, it is observed that argex concrete wall showed a better thermal performance with a higher time lag (6.218 h) and a lower decrement factor (0.5051). Mortar with silica fume showed a better thermal performance than a mortar with a higher time lag (0.60 h) and a lower decrement factor (0.991).

In this work, the temperature distribution in an indirect solar dryer chamber has been studied experimentally, where this chamber operates under the forced pregnancy influence. The experimental work aims to improve the temperature distribution in the solar dryer chamber, where the chamber is divided into two parts by an aluminum-coated polystyrene board, which has eight regularly distributed holes with a diameter of up to 2 cm. The obtained results confirmed that the panel improves the temperature distribution inside the solar dryer. The regularity of heat distribution in the upper part took a short period and this part is the largest. Despite its size compared to the lower part, the top part has the longest duration of heat distribution.

The objective of the present investigation is to do the theoretical thermodynamic analysis of various new eco-friendly R22 substitutes used in vapour compression refrigeration (VCR) cycle. In this work, nine mixture refrigerants were considered at different compositions. Thermodynamic properties of all the considered refrigerants were developed and the same properties were used in the performance analysis of alternative refrigerants. Standard VCR cycle was considered for the thermodynamic assessment of alternative refrigerants. The working conditions considered are expressed as Te = 7.2 °C, Tk = 54.4 °C, ΔTsup = 11.1 °C and ΔTsub = 8.3 °C, respectively. Results revealed that the COP of mixture refrigerant MR20 (R600a/R134a/R1270 5/47.5/47.5 in mass%) was 2.02% higher than the COP of R22 and other nine investigated refrigerants. Discharge temperature of compressor obtained for MR20 was 11.79 °C lower compared to that of R22. Compressor power obtained for MR20 was 1.96% lower than that of R22. Volumetric refrigeration capacity obtained for MR20 was relatively closer to that of R22. GWP100 of MR20 (619) was lower compared to the GWP100 of R22 (1760). Overall, the performance of mixture refrigerant MR20 was better compared to all the considered R22 alternatives, and therefore it might be an appropriate candidate to replace R22 used in air conditioners.

In this work, a blackened solar still has been fabricated and experimentally investigated for distillation of water. A tilted flat plate blackened-type solar still was designed for this purpose and fabricated. Solar still productivity is investigated by changing the input water quantity in the basin of the solar still. Indoor experimental testing was carried out. The effect of input water flow rate on the still productivity and purity of output water is investigated together. With the increase in quantity of input water, the solar still efficiency increases. The tests were conducted using the irradiance from a lamp array. It is found that 150 ml of distilled water is collected for a working period of 2 hours at 800 W input. An average overall efficiency of the designed solar still is found to be 7.95% for the 30 L of input water. With increase in water input to the solar still, its efficiency increases marginally. For the water input of 20 and 30 L, the solar still efficiencies are 7.41 and 7.95%, respectively. The quality of the distilled water is also determined experimentally and found to be satisfactory. Preliminary tests on the quality of distillate proved the possible use of the fabricated solar still for the production of distilled water for different uses in the college premises. By using the fabricated solar still, conductivity and TDS value of the sample water reduced significantly.

The solar air heater with a hemispherical shape obstacle has been introduced, and an experimental study has been conducted to explore their performance over an extensive scope of running environments. The collector efficiency can be enhanced by increasing the heat transfer surface area by incorporating fins or obstacles to either over or under the absorbing surfaces. Different operating conditions have been chosen to run the experimental setup. Various measurable parameters like temperature of absorbing plate, temperature of inlet and outlet air, temperature of ambient air and solar radiation have been measured. The mass flow rates in the flow channel duct have been changed and measured to conduct the experiments for study the variation in performance for both finned and smooth absorbing plates. The study was concluded with calculation of the collector efficiency and reported a significant improvement in efficiency with hemispherical fins on absorber plates.

Refrigeration system plays an important role in cooling/heating process in day-to-day life. Efficient and better design of a refrigeration system is useful for saving cost, energy and needful for the future application. The individual vapour compression refrigeration (VCR) and vapour absorption refrigeration (VAR) system have some drawbacks, so the research is carried out for dual cycle based on VCR-VAR system. NH3–LiNO3 VCR and VAR system in the single circuit allows more enhancements of efficiencies than individual VCR and VAR system-based cycles. The absorption cycles works with NH3–H2O system, and the vapour compression cycle works with NH3. The absorption cycles produces pure ammonia refrigerant, and the existing ammonia uses as a refrigerant for mechanical vapour compression plants.

The vapour absorption refrigeration system (VARS) as a future cooling–heating system to meet the energy crises and to replace the mechanical vapour compression systems (VCR) also utilized the waste and renewable energy. The different renewable energy sources uses as the driving source for the VARS are waste energy from the industrial exhaust heat or solar thermal energy to efficiently run, meet the cooling load capacity, and have lesser impact on the climate and the environment. Nowadays, the cost of electric power raising high and the change in climate require the system for more efficient design to make the system more compatible size which guides to save energy. Absorber is a vital component for a VARS, heat and mass transfer (HMT) analysis concern. Better design of absorber impacts on the absorption process, coefficient of performance (COP) of the VARS which reduces the shape and size absorber and generator sizes. The objective of this paper is to identify various enhancement techniques used for heat and mass transfer like absorber and generator and summarize the system performance, on experimental and numerical studies. The enhancement techniques are classified into passive and active methods; twisted tape, swirl generator, axial guide vane, internal grooved, internal and external fins, rotation of tube are the geometrical device used as a passive methods, and use of additives, nano-fluids, induced pulsation by cams, reciprocating plungers, vibrators, use of magnetic fields, etc., are the passive technique. Finally, the present literature database contains suggestions for future work for the absorber and generator for enhancement in the HMT in absorbers and performance of the VARS.

Preservation of food is major concern in India. In rural areas where electricity is not reached, clay pot is best option for preservation. The steady-state performance of clay pot is already carried out by considering cylindrical shape in the literature. But, in actual practice shape of the clay pot is curved; hence, it is necessary to study the curvature effect on the performance of clay pot refrigerator. For particular cooling load, the refrigeration temperature and geometrical dimensions can be predicted under various ambient conditions. Introduction of curvature in model reduces size of pot for the same refrigeration temperature. For a parabolic geometry, approximately 7–18% higher efficiency can be achieved as compared to cylindrical shape at same surface area for given atmospheric relative humidity and temperature. Also, overall size of model can be reduced. Hence, more compact model can be used for same heat transfer.

The thermal control of electronic devices is become an essential due to heavy uses in the modern world. To overcome this difficulty, the utilization of microchannel heat sink is an important device to cool the electronic circuits. So it is required for better understanding of the fluid flow and heat transfer in microchannel heat sink. Last two decades, a lot of investigation was carried out to improve the performance of the microchannel heat sink. The current paper deals with the study of conjugate heat transfer of a silicon-based microchannel heat by making a three-dimensional model. The 3-D model of microchannel heat sink consists of a silicon substrate of 10 mm length having rectangular cross section with different geometries. The impact of geometry on the distribution of temperature in the microchannel heat sink is presented and discussed by taking constant heat source and constant pumping power. This model was validated by comparing the obtained results with previously published papers on geometric optimization of a microchannel heat sink with liquid flow. A suitable geometric was found out by considering heat transfer, fluid flow keeping in mind of manufacturing the microchannel.

The main aim of this paper is to analyze the effect of speed of condenser fan motor on various parameters of vapor compression refrigeration system. A detailed study has been done on the performance of evaporator and the heat absorbing capacity of refrigerant when there is drop in temperature of the cooling space. The compressor being the work-consuming component, its performance has also been analyzed. The graph has been plotted between different temperatures and other parameters to understand the process. The experiment was conducted several times to confirm the results and performance. It was carried out by changing the condenser fan motor (CFM) speed with mentioning the reasons. Commercially used and freely available software, Cool Pack, is used to evaluate the refrigeration cycle performance. This also utilized to plot the p–h diagram and also to get the properties of the refrigerant R134a.

The fourth-largest railway network in the world, i.e. Indian Railways, operates more than 25,000 passenger trains everyday which consists of either ICF coaches or LHB coaches. Though the old ICF coaches generate the electricity to power the electrical things fitted inside it on its own, their productions have been stopped due to their ageing technology. They are now slowly replaced by modern Linke Hofmann Busch (LHB) coaches which are more reliable than the ICF coaches in almost every aspect except in the case of electricity generation. LHB coaches do not have self-electric generation systems; hence, they have to depend upon the End on Generation (EOG) or Head on Generation (HOG) system present in the train for supply of electricity inside the coaches. Nearly 90% of trains with LHB coaches are dependent on EOG system which consists of diesel generators which generates electricity for the train. This study investigates the use of solar photovoltaic (PV) modules which can be installed on top of train coaches and how it can be beneficial for an AC LHB coach. Many researchers have carried out their research for finding the capability of this type of electricity generation technique earlier. A comparative study has been carried out to find the economical way to supply electricity in the coach. This will not only help in the conservation of fuel, but also helps in significant reduction in noise and air pollution.

Today’s concern over drastic environmental degradation and depletion of reserve of fossil fuel have made the scientists to search for some renewable energy sources and advanced thermodynamic systems so that irreversibility can be minimized. Thermoelectric system has a great potential to generate electricity in the range of some microwatt to 500 W on the principle of Seebeck effect. It can also generate refrigerating effect ranging from 5 mW to 500 W on the principle of Peltier effect. It utilizes the waste heat from industry, motor vehicle or the solar energy. The efficiency of this system is determined from non-dimensional parameter Figure of Merit, ZT. Review of the updated research papers reveals the development of thermoelectric materials which give higher values of ZT so that system efficiency is increased. Enhancement of ZT is done by doping the bulk material with some other suitable one in nanostructural form. This decreases the lattice thermal conductivity and increases the power factor. As a result, ZT value of a thermoelectric material increases. System performance can be enhanced by properly utilizing the available heat. This is made possible by integrating photovoltaic cells with thermoelectric generator. Minimizing the resistances to heat flow and current flow through the thermoelectric modules and thermal resistance matching for thermoelectric cooling system also enhances the performance of a thermoelectric system. Development of thermoelectric cooling system run by thermoelectric generator, known as thermoelectric self-cooling system, draws more attention for the research as this technology gives a sustainable cooling system.

In conventional jaggery plants, the extracted sugarcane juice is used for preparing jaggery, while the residue bagasse is used as a fuel to meet the energy requirement. Normally, bagasse contains from 48 to 52% moisture which affects the calorific value of bagasse; hence, drying of bagasse is necessary. The heat required for the evaporation is provided by burning the bagasse in a pit-type furnace. It is crucial to maintain the level of moisture in bagasse used as a fuel in order to achieve high calorific value. In conventional jaggery plant, a large amount of heat is wasted inside the wall of the combustion chamber. The performance analysis is carried out for a newly designed portable jaggery plant. The bagasse drying mechanism of this plant recovers waste heat from the combustion chamber through walls. The heat transfer from combustion gases through a brick wall, metallic wall, porous wall, etc., are simulated through ANSYS software and are tried out to validate through experimentation with certain limitations. The experimental outcome reveals that about 3.5% waste heat from the combustion chamber removes 51% moisture from wet bagasse. Jaggery preparation utilizes 23% of the combustion chamber heat. Thus, a quick and non-laborious bagasse drying process alternative to conventional sun drying process is developed.