Optimized Performance of One-Bed Adsorption Cooling System

Adsorption cooling system can be driven by solar energy or waste heat, so it will effectively reduce fossil fuel consumptions when total system is well-designed. On the other hand, the system tends to have a large size, which will be an obstacle to install adsorption cooling systems to small to medium scale cooling demands, such as automobiles, houses, or shops. The study was aiming at the reduction of system size of adsorption cooling systems for refrigeration and air-conditioning applications. To simplify the system, we investigated one-bed configuration of adsorption cooling system. In general, one-bed adsorption cooling system would result in a large temperature fluctuation at chilled water outlet. To overcome that drawback and to maximize the cooling capacity, the cycle time, namely, pre-heating, desorption, pre-cooling, and adsorption times, of one-bed adsorption cooling system was optimized. In case of two-bed adsorption cooling system, two adsorbers operates in reverse phase each other, which means that the degree of freedom for cycle time optimization is two. In case of one-bed adsorption cooling sytem, four processes can be independently optimized. In our study, activated carbon-ethanol pair was chosen as the adsorbent-refrigerant pair because of a high adsorption capacity of activated carbons against ethanol. Using adsorption isotherms and kinetic data of activated carbon-ethanol pair measured by our research group, a lumped parameter model of one-bed adsorption cooling system was developed. The four parameters of cycle time were optimized using global optimization method, and the optimal time settings were effectively found. The results showed the effect of cycle time optimization on the cooling performance of one-bed adsorption cooling system

Performance Analysis of Solar Adsorption Cooling System - Effect of Position of Heat Storage Tank

An insulated storage tank has been added with adsorption cooling system run by solar heat collected by CPC panel. It has been expected and seen that the storage tank has a vital contribution in the performance of the chiller. The storage tank is connected with a solar heat driven single stage two bed basic adsorption chillers activated with silica gel-water pair in two ways. The tank is connected in such a way that (i) the solar collectors supply hot water to the desorption bed, the outflow of the desorber is collected in the reserve tank. The reserve tank supplies water to the collector and complete the heat transfer cycle. (ii) The solar collector supply hot water which is collected in the storage tank first and then supplied to the desorber. The outflow of the desorber is carried to the collector again. Comparative studies have been conducted at the steady state for both of the systems with heat storage. It has been observed that the system is robust with design (i) while with design (ii) performance enhances beyond the sunset time with heat storage

Nano-refrigerants and nano-lubricants in refrigeration : synthesis, mechanisms, applications, and challenges

Addressing global energy security and environmental concerns, the utilization of nano-refrigerants and nano-lubricants has emerged as an innovative path for enhancing heat transfer. This research focuses on enhancing the thermophysical properties, heat transfer efficiency, and tribological characteristics of nanofluids—nanoparticles dispersed in refrigerants or lubricants. These nanofluids have demonstrated significant potential in applications such as cooling, air conditioning systems, and heat transfer equipment including pumps and pipes. A comprehensive understanding of parameters like thermal conductivity, viscosity, pressure drop, pumping power, and energy performance is delivered, with the aim of enhancing the overall efficiency of refrigeration systems, particularly the coefficient of performance (COP). Additionally, the review covers existing research on flow and pool boiling heat transfer, nano-lubricant tribological enhancement, and nano-refrigerant condensation. The study also addresses the challenges associated with the use of nano-refrigerants and nano-lubricants and offers a prospective outlook for their usage. These novel nanofluids are anticipated to emerge as effective solutions for increasing the COP and reducing energy consumption in the industrial sector, thus extending beyond the scope of previous efforts in this field. This review could serve as a valuable resource for a broad audience interested in this novel approach to energy efficiency

ICAR: endoscopic skull‐base surgery

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Study of an innovative combined absorption-adsorption cooling system employing the same evaporator and condenser

In this paper, the performance of innovative combined absorption and adsorption cooling (ABC-ADC) systems employing the same evaporating and condensing units is theoretically investigated. The generator of the absorption cooling (ABC) system is connected directly to the heat source system, and the outlet hot water is used to drive the desorber bed of the adsorption cooling (ADC) system. The performance of the proposed system is compared with a separated ABC-ADC system, combined ABD-ADC employing the parallel operation mode, conventional single-stage ADC cycle, and other integrated systems available in the literature. In the separated system, each system of ABC and ADC has its condenser and evaporator. Results showed that, at 85 °C heat source temperature, the cooling capacity and COP of the proposed combined ABD-ADC configuration are 0.344 kW and 0.623, respectively, and higher than that of the separated ABC, and ADC systems by 4.06% and 2.73%, respectively. The cooling capacity and COP of the proposed combined ABD-ADC configuration are significantly higher than that of the single-stage ADC system by 58.34% and 27.07%, respectively. The outlet chilled water temperature fluctuation of the proposed combined ABC-ADC systems (±0.88 °C) is significantly lower than that of the separated ABC-ADC system (±1.84 °C). Validation of the proposed ABC and ADS mathematical models with other published experimental data are around 0.2% and ±10% respectively

Thermodynamic Analysis of Adsorption Refrigeration Cycles Using Parent and Surface Treated Maxsorb III/Ethanol Pairs

Adsorption equilibrium uptake of environment friendly refrigerant ethanol onto highly porous activated carbon based adsorbents has been experimentally investigated by using a magnetic suspension balance adsorption measurement unit (MSB-VG-S2). Adsorbents used in the present study are parent Maxsorb III, H2 and KOH-H2 surface treated Maxsorb III. Experiments have been conducted over adsorption temperatures range from 30 to 70 ºC and evaporation temperatures between -6 and 65 ºC. The Dubinin-Radushkevich and Dubinin-Astakhov adsorption isotherm models have been used to correlate adsorption isotherm data and to plot the pressure-temperature-concentration (P-T-W) diagrams of the assorted pairs. Isosteric heat of adsorption is estimated using the Clausius–Clapeyron equation. In the present study, the performance of adsorption refrigeration cycles using activated carbons/ethanol pairs has also been investigated employing a time-independent mathematical model. Results are compared with other adsorbent/refrigerant pairs found in the open literatures. Theoretical analysis show that the H2-treated Maxsorb III/ethanol adsorption refrigeration cycle can achieve coefficient of performance (COP) of 0.51 and specific cooling effect of about 374 kJ/kg at the evaporator temperature of -5 ºC in combination with heat source and heat sink temperatures of 100 and 30 ºC, respectively

Accurate adsorption isotherms of R134a onto activated carbons for cooling and freezing applications

The objective of this article is to improve the performance of thermally powered adsorption/cooling systems by selecting a new adsorbent/refrigerant pair. Adsorption equilibrium data of R134a onto granular activated carbon (AC) and Unitika activated carbon fiber (ACF) of type (A-20) have been measured experimentally using Rubotherm ISOSORP 2000 within evaporation temperatures range between −20 and 40 °C and adsorption temperatures range from 30 to 80 °C. Experimental data have been correlated using various popular isotherm models. The isosteric heat of adsorption of the assorted adsorbent/refrigerant pairs has also been extracted from the present experimental data

Influence of a Hybrid MPPT Technique, SA-P&O, on PV System Performance under Partial Shading Conditions

The electricity sector has been undergoing profound transformations. In particular, the Portuguese self-consumer regime has allowed customers of the medium and low voltage electricity grid to be producers/consumers of electricity, actively contributing to greater energy efficiency. In this context, the energy that comes from the sun is not used to its maximum. In addition, photovoltaic cells have a characteristic operating curve (voltage vs. current), in which any operating point is reflected. Within this curve, there is a particular point known as the maximum power point (MPP) at which the cell supplies the maximum power output to a load. If the cell does not operate at this point, it has lower efficiency values. To harness maximum power under standard and dynamic shading conditions, there are various techniques of low complexity for capturing maximum power. We present a maximum power point tracking (MPPT) algorithm capable of dealing with the problem of partial shading. This algorithm involves modifying one of the most used algorithms within photovoltaic systems, known as P&O, using a simulated annealing (SA) algorithm. P&O is often used due to its straightforward implementation, but it is susceptible to partial shade conditions. Sampling was added to this algorithm to a better approach to the point of maximum power using the SA, and then to attain a more precise convergence with P&O. Implementing a maximum power point tracking method under partial shading was the major goal of this study