Mechanical Compression Refrigeration Systems Research Articles

Investigation on the Ammonia Boiling Heat Transfer Coefficient in Plate Heat Exchangers

This investigation aims to compare the experimental and theoretical ammonia boiling heat transfer coefficient in a plate heat exchanger (PHE). Measured data were gathered during functioning of a single stage vapor mechanical compression refrigeration system placed in the Thermal Systems Research Center of the Technical University of Civil Buildings Bucharest (TUCEB). Experimental values fall within the range of 1377–3050 W/m2K. Theoretical values were obtained from 12 correlations confirmed by the literature to date, developed for similar working conditions. The experimental values are close to the theoretical ones for Shah and Jokar correlations applied for a vapor quality of 0.5. The theoretical values are in the range of 1440–2076 W/m2K and 1558–2318 W/m2K, respectively. Shah correlation predicted 82.35% of all data within the ±30% error band at an MAE value of 14.23%, and Jokar et al. predicted 76.47% of all data within the ±30% error band with an MAE value of 17.7%.

Optimal control analysis and Practical NMPC applied to refrigeration systems

This work is focused on optimal control of mechanical compression refrigeration systems. A reduced-order state-space model based on the moving boundary approach is proposed for the canonical cycle, which eases the controller design. The optimal cycle (that satisfying the cooling demand while maximizing efficiency) is defined by three variables, but only two inputs are available, therefore the controllability of the proposed model is studied. It is shown through optimization simulations how optimal cycles for a range of the cooling demand turn out not to be achieved by keeping the degree of superheating to a minimum. The Practical NMPC and a well-known feedback-plus-feedforward strategy from the literature are compared in simulation, both showing trouble in reaching the optimal cycle, which agrees with the controllability study.

Design of eco-friendly refrigeration system

The present study of a freezing system has developed based on an air conditioning system, whose purpose is to take advantage of the technological transfer of cold producing equipment for food storage and conservation uses. The installed capacity of 9000 BTU/Hr was considered for the choice of equipment. We studied the freezing process of fish, water, and the preservation of legumes with a volume of 1 kg per product individually. The freezing temperature has evaluated with a mechanical compression refrigeration system of Gas R22 with temperature interactions of 29.6 ° C to -12 ° C. and monitored with a Proportional Integrative Derivative (PID) controller. For production cost, the equipment was mostly made of its parts and pieces with recycling material. A descriptive experimental design has carried out, for the verification of results. The equipment managed to reach chamber temperatures of -13 ° C from 20 minutes once the equipment (compressor) has turned on under specific product descriptions.

Optimization analysis of a hybrid fresh air handling system based on evaporative cooling and condensation dehumidification

This paper studies a fresh air handling system, which is composed of a mechanical compression refrigeration system and an evaporative cooling system. In an effort to improve the basic systems, a single-stage total heat recovery module consisting of a cooler and a spray packing is incorporated into the system (process I). The results show that when keeping the total heat and mass transfer capability constant, the coefficient of performance (COP) of process I first increases and then decreases with increasing heat and mass transfer capability of the total heat recovery module. Under typical summer conditions, the optimum COP of process I is 8.5% higher than that of the conventional system. To reduce the exergy destruction in the total heat recovery module and increase the supply air temperature, a single-stage sensible heat recovery module is also incorporated (process II), leading to a further increase in the optimum COP of 3.3% and suitable supply air temperature. A test device based on process II was constructed to experimentally validate the simulation results. The experimental results demonstrate that the system performance is better for high temperature and humidity fresh air conditions owing to the higher proportion of total heat recovery.

Optimized coupling analysis of Internal Combustion Engine (ICE)-ORC-MCRS

This paper refers to recovering of waste heat from hot gases discharged by internal combustion engines (ICE) at partial or full load using a Rankine Organic (ORC) cycle which drives a compressor of a mechanical compression refrigeration system (MCRS) to convert heat recovered into cooling power. The subject is of particular interest to the automotive and refrigeration industry with the aim of finding a feasible solution for the recovery of residual heat and turning it into a real source of commercial or industrial refrigeration. The heat recovery system is based on an ORC driven by SES36, a working fluid with good thermodynamic properties for the recovery of low temperature heat, as well as refrigeration or air conditioning refrigeration cycles. A scheme was proposed that combines the two systems so as to use the same working fluid, thus using a small number of subassemblies. After the energetic and exergetic calculations, it was proved that the ICE-ORC-MCRS system is of real interest due to the recorded performances, while the optimization of the thermodynamic scheme can be upgraded by improving the heat transfer at the level of the exchangers, but also constructively trying to streamline the scheme with new heat recovery.

Experimental Study on Performance of Solar Thermal Driven Cooling System Versus a Hybrid Mechanical Compression Refrigeration-Solar Thermal Assisted System in Hot Areas

Refrigeration and air conditioning systems are essential requirements for human needs, and, this followed by an increasing demand for electric energy. The recent trend in research and development find such systems to be driven entirely or partiality by renewable energy. One goal of this study is to minimize the grid-based electrical power needed by the residential scale air conditioning system through either using full, driven or partiality solar thermal energy. The study main aim is to present the reduction in the electrical power consumption by the mechanical compression refrigeration system through integrating an intermediate solar thermal to raise the pressure of the refrigerant after the compressor and before the condenser and to compare this system performance with an entirely driven solar thermal cooling system under hot, arid areas. This is being done through design, constructing and operation of both systems and carrying out the performance measurements under Assiut city environmental conditions.

Energetic and exergetic investigation of a novel solar assisted mechanical compression refrigeration system

The objective of this study is to present and to examine a novel solar assisted mechanical compression refrigeration system. Evacuated tube collectors are used in order to partially thermally compress the refrigerant, after the mechanical compressor. This design aims to reduce the electricity consumption using a renewable energy source, creating a sustainable system. The suggested design is analyzed parametrically in order to investigate its energetic and exergetic behaviour in various operating conditions and it is examined with EES (Engineering Equator Solver) in steady state conditions. The temperature levels in the evaporator and in the condenser, as well as the thermal compression fraction (expressed with the pressure ratio parameter), are the examined parameters. The final results proved that the optimum values of the pressure after the mechanical compressor is the 75% of the maximum pressure and for this case, energy savings from 15% to 25% can be achieved. Moreover, the specific collecting area is found to be relatively low, close to 2m2/kW for the optimum cases. The final results proved that the new design leads to energy savings in all the examined cases and especially in cases with higher evaporating temperature levels, a fact that makes it ideal for space cooling applications.

Electricity Reduction in Building Climatisation in Hot and Humid Climate Through the Use of Solar Desiccant Wheel

We studied with numerical simulation the amount of energy and costs reduction obtained with the use of a desiccant system combined with other cooling alternatives in the air conditioning of a regular office building in the Brazilian city of Belém, where the climate is hot and humid most of the year. Five different air handling processes using desiccant wheel were analyzed and compared with a standard one, which was assumed as the conventional mechanical compression air conditioner without desiccant wheel. Solar energy was one of the alternatives studied to provide the regeneration heat of the desiccant wheel. Natural gas was chosen as auxiliary heater when the solar energy was not enough to regenerate the wheel. Beside the desiccant wheel, the cooling system also comprised either an evaporative cooling equipment or a mechanical compression system. The results indicated that, although the desiccant system removed the latent heat of the total cooling load, the regeneration energy load was larger than the energy consumption of the mechanical compression system. The use of solar energy to regenerate the desiccant wheel is necessary to guarantee the economical feasibility for the system operation. In this case, the use of a desiccant wheel combined with a mechanical compression refrigeration system and an evaporative cooling equipment was the arrangement with smaller operational cost.