scholarly journals Experimental Study of Condensation in a Thermoacoustic Cooler With Various 3D-Printed Regenerators Using Water Vapor as the Working Fluid

2019 ◽  
Vol 142 (5) ◽  
Author(s):  
Aibek Bekkulov ◽  
Andrew Luthen ◽  
Ben Xu
Keyword(s):  
Water Vapor ◽  
Low Temperature ◽  
Temperature Gradient ◽  
Sound Wave ◽  
Cooling Capacity ◽  
Working Fluid ◽  
Cooling Power ◽  
Parallel Plates ◽  
Humid Air ◽  
Condense Water

Abstract Thermoacoustics (TA) deals with the conversion of heat into sound and vice versa. The device that transfers energy from a low-temperature reservoir to a high-temperature one by utilizing acoustic work is called TA cooler (TAC). The main components of a typical TAC are a resonator, a porous regenerator (e.g., stack of parallel plates), and two heat exchangers. The thermoacoustic phenomenon takes place in the regenerator where a nonzero temperature gradient is imposed and interacts with the sound wave. The low temperature at the cold end of TAC can be used to condense water from the humid air and also reduce the moisture. In the current study, the sound wave with high intensity was produced to drive a TAC to produce cooling power at a cold temperature around 18 °C, using saturated water vapor as the working fluid. The drainage of condensate in the regenerator is the key to the system’s performance. This work is dedicated to investigate the effect from temperature gradient created in TAC on the condensation enhancement, by adopting three different designs of regenerators. A 3D printer was used to design and fabricate different structures of regenerator, and then, the systematic cooling capacity was tested and compared with different regenerators. This work can be extended to evaluate how the TA effect can be affected by the condensation if humid air is directly used as the working fluid. The potential application of this investigation can be an autonomous TAC system for water harvesting in arid areas.

Experimental Study of Condensation in Different 3D Printed Regenerators in a Thermoacoustic Cooler

2019 ◽  
Author(s):  
Aibek Bekkulov ◽  
Andrew Luthen ◽  
Ben Xu
Keyword(s):  
Low Temperature ◽  
Temperature Gradient ◽  
Sound Wave ◽  
Cooling Capacity ◽  
Working Fluid ◽  
Cooling Power ◽  
Sound Waves ◽  
Parallel Plates ◽  
Main Components ◽  
Thermoacoustic Cooler

Abstract Thermoacoustics (TA) deals with the conversion of heat into sound and vice versa. The device that transfers energy from a low temperature reservoir to a high temperature one by utilizing acoustic work is called TA cooler (TAC). The main components of a typical TA device are a resonator, a regenerator (stack of parallel plates) and two heat exchangers. The thermoacoustic phenomenon takes place in the stack when a nonzero temperature gradient imposed along the regenerator (i.e. parallel to the direction of the sound wave propagation) interacts with the sound wave oscillations. The low temperature at the cold of TAC can be used to condense humid water from the air and also reduce the moisture in the air at some humid areas. In the current study, the high intensity sound waves was produced by the speaker to drive a TA cooler to produce cooling power at a cold temperature of around 18°C. The drainage of condensate in the regenerator is the key for the system performance, because if the porous structure will be blocked by the condensate, TA phenomenon cannot take place in the regenerator. This work is dedicated to investigate the effect from temperature gradient created in TAC for condensation enhancement. 3D printer was used to design and fabricate different structures of regenerator, and then the systematic cooling capacity was measured and compared with different designs of regenerators. Energy balance was also discussed for each type of regenerator. The potential application of this investigation can be an autonomous thermoacoustic cooler system for water harvesting in arid areas. This work can be used to evaluate how the TA effect can be affected by the condensation if humid air is used as the working fluid.

Performance Evaluations of Extracting Water From Dry Air Using Multi-Stage Desiccant Wheels and Vapor Compression Cycle

2019 ◽  
Author(s):  
Rang Tu ◽  
Lanbin Liu
Keyword(s):  
Water Vapor ◽  
Energy Consumption ◽  
High Temperature ◽  
Low Temperature ◽  
Rural Areas ◽  
Waste Heat ◽  
Dew Point ◽  
Solid Adsorbent ◽  
Multi Stage ◽  
Condense Water

Abstract A water extraction device that takes water from air in dry area is proposed. This device is designed to meet domestic water demand in remote rural areas, where the climate is dry and fresh water is scarce. The device can be driven effectively by low-temperature waste heat and has the characteristics of large daily water production, low energy consumption per unit of water and high water quality. Because the moisture content of air in dry area is very low, the effect of direct condensation is limited. Solid adsorbent is able to adsorb water vapor from air at a low temperature and release water vapor at under high temperature, which can be used for water extracting from air. To improve its performance under dry circumstances, the key technical point of this device is to use solid adsorbent to collect water vapor from other air to raise its dew point temperature, and then use high temperature cold source to condense water vapor from it. In this paper, configurations of the solid adsorption are proposed, which can be driven with low regeneration temperature under the same humidity increasing amount. This device uses multi-stage desiccant wheels to realize humid increasing. Desiccant wheel can be driven with high temperature to take water vapor from dehumidification air and release water vapor to regeneration air. The multi-stage configuration is good for the reduction of regeneration temperature, making applications of low temperature waste heat form heat pumps possible. Then, influencing factors of water extracting rate are analyzed. The influencing of regeneration temperature, humid reduction amount of the humidified air and cooling and heating systems, etc., are analyzed. Last, air handling processes considering cold and heat sources are recommended to reduce energy consumption. The heat pump driven scenarios are discussed in particular. Through optimization, the water extracting rate can be increased and energy consumption per unit of water can be reduced. At present, this paper only studies air water extracting processes and thermal processes, and does not involve structure of the device, water purification and power consumption of fans, etc.

scholarly journals Numerical Simulation of Oscillating Multiphase Heat Transfer in Parallel Plates Using Pseudopotential Multiple-Relaxation-Time Lattice Boltzmann Method

2018 ◽  
Author(s):  
Wandong Zhao ◽  
Ben Xu ◽  
Ying Zhang
Keyword(s):  
Relaxation Time ◽  
Lattice Boltzmann ◽  
Multiphase Flows ◽  
Saturated Vapor ◽  
Working Fluid ◽  
Oscillating Flow ◽  
Tensor Model ◽  
Parallel Plates ◽  
Humid Air ◽  
Multiple Relaxation Time

Multiphase flows frequently occur in many important engineering and scientific applications, but modeling of such flows is a rather challenging task due to complex interfacial dynamics between different phases, let alone if the flow is oscillating in the porous media. Using humid air as the working fluid in the thermoacoustic refrigerator is one of the research focus to improve the thermoacoustic performance, but the corresponding effect is the condensation of humid air in the thermal stack. Due to the small sized spacing of thermal stack and the need to explore the detailed condensation process in oscillating flow, a mesoscale numerical approach need to be developed. Over the decades, several types of Lattice Boltzmann (LB) models for multiphase flows have been developed under different physical pictures, for example the color-gradient model, the Shan-Chen model, the nonideal pressure tensor model and the HSD model. In the current study, a pseudopotential Multiple-Relaxation-Time (MRT) LBM simulation was utilized to simulate the incompressible oscillating flow and condensation in parallel plates. In the initial stage of condensation, the oscillating flow benefits to accumulate the saturated vapor at the exit regions, and the velocity vector of saturated vapor clearly showed the flow over the droplets. It was also concluded that if the condensate can be removed out from the parallel plates, the oscillating flow and condensation will continuously feed the cold surface to form more water droplets. The effect of wettability to the condensation was discussed, and it turned out that by increasing the wettability, the saturated water vapor was easier to condense on the cold walls, and the distance between each pair of droplets was also strongly affected by the wettability. It’s expected that this study can be used to optimize and redesign the structure of thermal stack in order to produce more condensed water, also this multiphase approach can be extended to more complicated 3D structures.

Experimental Investigation of an Ammonia-Water Diffusion-Absorption Refrigerator (DAR) at Part Load

2017 ◽  
Author(s):  
Ahmad Najjaran Kheirabadi ◽  
James Freeman ◽  
Alba Ramos Cabal ◽  
Christos N. Markides
Keyword(s):  
Heat Source ◽  
Heat Supply ◽  
Cooling Capacity ◽  
Working Fluid ◽  
Cooling Power ◽  
Ammonia Water ◽  
Part Load ◽  
Thermally Driven ◽  
Cold Box ◽  
Diffusion Absorption

Diffusion absorption refrigeration (DAR) cycles enable passive fully thermally-driven refrigeration for off-grid purposes. Typically, DAR units are designed for a given heat supply load and temperature, although real operation inevitably involves unsteady variations in these inputs. In this study, a thermally-driven DAR unit with a nominal cooling capacity of 120 W is connected to an electric heat source. The working fluid is ammonia-water NH3/H2O, with hydrogen (H2) added as an auxiliary gas to keep the system pressure constant and to decrease the partial pressure of the refrigerant (ammonia) in the evaporator. A control unit is used to adjust and measure the input heat-source power applied to the unit. The operating pressure of the system is 20.7 bar, the ambient temperature is 22 °C and the input thermal power is in the range 250 to 700 W. The cooling capacity of the unit and the input heat load are measured simultaneously at different operation conditions. To measure the cooling power, a cold box is constructed around the evaporator, and a second heater is located inside the cold box which sets the cold space temperature equal to that of the ambient. This allows the coefficient of performance (COP) to be evaluated. The COP and cooling capacity of the unit are investigated at part load by varying the heat supply, from which maximum values are obtained (0.28 and 110 W, respectively). Finally, experimental results are compared to the theoretical predictions from a thermodynamic model of a DAR cycle. Once validated, the model is also used to find the properties of the fluid mixture in different states in the DAR cycle.

Technical Note. Influence of Material Used for the Regenerator on the Properties of a Thermoacoustic Heat Pump

2013 ◽  
Vol 38 (4) ◽  
pp. 565-570 ◽  
Author(s):  
Bartłomiej Kruk
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Acoustic Wave ◽  
Heat Pump ◽  
Sound Wave ◽  
Heat Exchangers ◽  
Heat Pumps ◽  
Technical Note ◽  
New Materials ◽  
Modern Technologies

Abstract Research in termoacoustics began with the observation of the heat transfer between gas and solids. Using this interaction the intense sound wave could be applied to create engines and heat pumps. The most important part of thermoacoustic devices is a regenerator, where press of conversion of sound energy into thermal or vice versa takes place. In a heat pump the acoustic wave produces the temperature difference at the two ends of the regenerator. The aim of the paper is to find the influence of the material used for the construction of a regenerator on the properties of a thermoacoustic heat pump. Modern technologies allow us to create new materials with physical properties necessary to increase the temperature gradient on the heat exchangers. The aim of this paper is to create a regenerator which strongly improves the efficiency of the heat pump.

scholarly journals Developing a Cold Accumulator with a Capsule Bed Containing Water as a Phase-Change Material

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2703
Author(s):  
Robert Sekret ◽  
Przemysław Starzec
Keyword(s):  
Energy Efficiency ◽  
Heat Pump ◽  
Cold Storage ◽  
Cooling Capacity ◽  
Cooling Power ◽  
Storage Process ◽  
Water Ice ◽  
Measurement Results ◽  
Mathematical Relationships ◽  
Change Material

The paper presents the investigation of a prototype cold accumulator using water–ice latent heat for the cold storage process. The concept of the cold accumulator was based on a 200-L-capacity cylindrical storage tank in which spherical capsules filled with water were placed. Beds of polypropylene capsules with diameters of 80 mm, 70 mm, and 60 mm were used in the tests. The cold accumulator operated with a water–air heat pump. Based on the test results, the following parameters were calculated: the cooling capacity, cooling power, energy efficiency of the cold storage, and energy efficiency ratio (EER) of the accumulator. The obtained measurement results were described with mathematical relationships (allowing for measurement error) using criterial numbers and the developed “Research Stand Factor Number” (RSFN) index. It has been found that, for the prototype cold accumulator under investigation, the maximum values of the cooling capacity (17 kWh or 85.3 kWh per cubic meter of the accumulator), energy efficiency (0.99), and EER (4.8) occur for an RSFN of 144·10−4. The optimal conditions for the operation of the prototype cold accumulator were the closest to laboratory tests conducted for a bed with capsules with a diameter of 70 mm and a mass flow of the water–glycol mixture flowing between the accumulator and the heat pump of 0.084 kg/s. During the tests, no significant problems with the operation of the prototype cold accumulator were found.

Thermodynamic analysis of triple effect ammonia–water absorption compression (hybrid) cycle

2021 ◽  
pp. 095440892199568
Author(s):  
CP Jawahar
Keyword(s):  
Water Absorption ◽  
Energy Analysis ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Performance Parameters ◽  
Evaporator Temperature ◽  
Ammonia Water ◽  
Absorption Cycle ◽  
Hybrid Cycle

This paper presents the energy analysis of a triple effect absorption compression (hybrid) cycle employing ammonia water as working fluid. The performance parameters such as cooling capacity and coefficient of performance of the hybrid cycle is analyzed by varying the temperature of evaporator from −10 °C to 10 °C, absorber and condenser temperatures in first stage from 25 °C to 45 °C, degassing width in both the stages from 0.02 to 0.12 and is compared with the conventional triple effect absorption cycle. The results of the analysis show that the maximum cooling capacity attained in the hybrid cycle is 472.3 kW, at 10 °C evaporator temperature and first stage degassing width of 0.12. The coefficient of performance of the hybrid cycle is about 30 to 65% more than the coefficient of performance of conventional triple effect cycle.

Popcorn-like aluminum-based powders for instant low-temperature water vapor hydrogen generation

2020 ◽  
pp. 100602
Author(s):  
Xinren Chen ◽  
Cuiping Wang ◽  
Yuheng Liu ◽  
Yansong Shen ◽  
Qijun Zheng ◽  
...  
Keyword(s):  
Water Vapor ◽  
Low Temperature ◽  
Hydrogen Generation ◽  
Temperature Water
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