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.

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.

A Parametric Examination of the Factors Affecting the Performance of a Diffusion Absorption Refrigeration System

2021 ◽  
pp. 1-38
Author(s):  
Noman Yousuf ◽  
Timothy Anderson ◽  
Roy Nates
Keyword(s):  
Waste Heat ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Low Grade ◽  
Absorption Refrigeration ◽  
Factors Affecting ◽  
Thermally Driven ◽  
Mass Flowrate ◽  
Diffusion Absorption

Abstract Despite being identified nearly a century ago, the diffusion absorption refrigeration (DAR) cycle has received relatively little attention. One of the strongest attractions of the DAR cycle lies in the fact that it is thermally driven and does not require high value work. This makes it a prime candidate for harnessing low grade heat from solar collectors, or the waste heat from stationary generators, to produce cooling. However, to realize the benefits of the DAR cycle, there is a need to develop an improved understanding of how design parameters influence its performance. In this vein, this work developed a new parametric model that can be used to examine the performance of the DAR cycle for a range of operating conditions. The results showed that the cycle's performance was particularly sensitive to several factors: the rate of heat added and the temperature of the generator, the effectiveness of the gas and solution heat exchangers, the mass flowrate of the refrigerant and the type of the working fluid. It was shown that can deliver good performance at low generator temperatures if the refrigerant mass fraction in the strong solution is made as high as possible. Moreover, it was shown that a H2O-LiBr working pair could be useful for achieving cooling at low generator temperatures.

scholarly journals A Compact Thermally Driven Cooling System Based on Metal Hydrides

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2482 ◽  
Author(s):  
Christoph Weckerle ◽  
Marius Dörr ◽  
Marc Linder ◽  
Inga Bürger
Keyword(s):  
Internal Combustion Engines ◽  
Cooling System ◽  
Heating System ◽  
Operating Conditions ◽  
Specific Power ◽  
Working Fluid ◽  
Cooling Power ◽  
Half Cycle ◽  
Exhaust Heat ◽  
Thermally Driven

Independent of the actual power train, efficiency and a high driving range in any weather conditions are two key requirements for future vehicles. Especially during summertime, thermally driven air conditioning systems can contribute to this goal as they can turn the exhaust heat of internal combustion engines, fuel cells or of any additional fuel-based heating system into a cooling effect. Amongst these, metal hydride cooling systems (MHCSs) promise very high specific power densities due to the short reaction times as well as high reaction enthalpies. Additionally, the working fluid hydrogen has a very low global warming potential. In this study, the experimental results of a compact and modular MHCS with a specific cooling power of up to 585 W kg MH − 1 referred to one cold generating MH are presented, while reactor and MH weight in total is less than 30 kg and require a volume < 20 dm3. The system is driven by an auxiliary fuel heating system and its performance is evaluated for different operating conditions, e.g., temperature levels and half-cycle times. Additionally, a novel operation optimization of time-shifted valve switching to increase the cooling power is implemented and investigated in detail.

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.

215 Experimental Study Influence of Heat Source Conditions on OTEC System Using Ammonia/Water Mixture as Working Fluid

2006 ◽  
Vol 2006 (0) ◽  
pp. 71-72
Author(s):  
Yasuyuki IKEGAMI ◽  
Hiroyuki ASOU ◽  
Takeshi YASUNAGA ◽  
Hirokazu MANDA ◽  
Kaori KUBO
Keyword(s):  
Experimental Study ◽  
Heat Source ◽  
Working Fluid ◽  
Water Mixture ◽  
Ammonia Water

Experimental Investigations of Oscillatory Fluctuation in an Ammonia-Water Mixture Turbine System

2005 ◽  
Author(s):  
Yoshiharu Amano ◽  
Keisuke Kawanishi ◽  
Takumi Hashizume
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Flow Rate ◽  
Mass Fraction ◽  
Working Fluid ◽  
Experimental Investigations ◽  
Water Mixture ◽  
Kalina Cycle ◽  
Ammonia Water ◽  
Temperature Heat

This paper reports results from experimental investigations of the dynamics of an ammonia-water mixture turbine system. The mixture turbine system features Kalina Cycle technology [1]. The working fluid is an ammonia-water mixture (AWM), which enhances the power production recovered from the low-temperature heat source [2], [3]. The Kalina Cycle is superior to the Rankine Cycle for a low temperature heat source [4], [5]. The ammonia-water mixture turbine system has distillation-condensation processes. The subsystem produces ammonia-rich vapor and a lean solution at the separator, and the vapor and the solution converge at the condenser. The mass balance of ammonia and water is maintained by a level control at the separator and reservoirs at the condensers. Since the ammonia mass fraction in the cycle has a high sensitivity to the evaporation/condensation pressure and vapor flow rate in the cycle, the pressure change gives rise to a flow rate change and then level changes in the separators and reservoirs and vice versa. From the experimental investigation of the ammonia-water mixture turbine system, it was observed that the sensitivity of the evaporating flow rate and solution liquid density in the cycle is very high, and those sensitivity factors are affected by the ammonia-mass fraction. This paper presents the experimental results of a study on the dynamics of the distillation process of the ammonia-water mixture turbine system and uses the results of investigation to explain the mechanism of the unstable fluctuation in the system.

scholarly journals Operational Optimisation of a Non-Recuperative 1-kWe Organic Rankine Cycle Engine Prototype

2019 ◽  
Vol 9 (15) ◽  
pp. 3024 ◽  
Author(s):  
Chinedu K. Unamba ◽  
Paul Sapin ◽  
Xiaoya Li ◽  
Jian Song ◽  
Kai Wang ◽  
...  
Keyword(s):  
Steady State ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Electric Heater ◽  
Part Load ◽  
Source Temperature ◽  
Heat Source Temperature

Several heat-to-power conversion technologies are being proposed as suitable for waste-heat recovery (WHR) applications, including thermoelectric generators, hot-air (e.g., Ericsson or Stirling) engines and vapour-cycle engines such as steam or organic Rankine cycle (ORC) power systems. The latter technology has demonstrated the highest efficiencies at small and intermediate scales and low to medium heat-source temperatures and is considered a suitable option for WHR in relevant applications. However, ORC systems experience variations in performance at part-load or off-design conditions, which need to be predicted accurately by empirical or physics-based models if one is to assess accurately the techno-economic potential of such ORC-WHR solutions. This paper presents results from an experimental investigation of the part-load performance of a 1-kWe ORC engine, operated with R245fa as a working fluid, with the aim of producing high-fidelity steady-state and transient data relating to the operational performance of this system. The experimental apparatus is composed of a rotary-vane pump, brazed-plate evaporator and condenser units and a scroll expander magnetically coupled to a generator with an adjustable resistive load. An electric heater is used to provide a hot oil-stream to the evaporator, supplied at three different temperatures in the current study: 100, 120 and 140 ∘ C. The optimal operating conditions, that is, pump speed and expander load, are determined at various heat-source conditions, thus resulting in a total of 124 steady-state data points used to analyse the part-load performance of the engine. A maximum thermal efficiency of 4.2 ± 0.1% is reported for a heat-source temperature of 120 ∘ C, while a maximum net power output of 508 ± 2 W is obtained for a heat-source temperature at 140 ∘ C. For a 100- ∘ C heat source, a maximum exergy efficiency of 18.7 ± 0.3% is achieved. A detailed exergy analysis allows us to quantify the contribution of each component to the overall exergy destruction. The share of the evaporator, condenser and expander components are all significant for the three heat-source conditions, while the exergy destroyed in the pump is negligible by comparison (below 4%). The data can be used for the development and validation of advanced models capable of steady-state part-load and off-design performance predictions, as well as predictions of the transient/dynamic operation of ORC systems.

Design and Experimental Investigation of a Diffusion Absorption Refrigeration System

2006 ◽  
Author(s):  
Shiming Xu ◽  
Jian Liang ◽  
Yi Jian He ◽  
Ru Xu Du
Keyword(s):  
Cooling Capacity ◽  
Input Power ◽  
Experimental Results ◽  
Working Fluid ◽  
Absorption Refrigeration ◽  
Operation Condition ◽  
Operation Conditions ◽  
System Pressure ◽  
Diffusion Absorption ◽  
Bubble Pump

This paper presents the design and experimental analysis of a compact Diffusion Absorption Air Cooler (DAAC) system, in which the Diffusion Absorption Refrigeration (DAR) technology is utilized. The system uses a bubble pump to replace the mechanical pump, uses three-component working fluid (NH3+H2O+He), and operates under the same system pressure level. Hence, it is quiet, long lasting and environmental friendly. To investigate the practicality of using the DAAC system for regional air conditioning, the thermodynamic model is derived to guide the system design first, and then a DAAC experimental prototype is built for validation. Since the bubble pump is the kernel component, a series of experiments are conducted to investigate the bubble pump performance. From the experimental results under various operation conditions, it is found that the bubble pump dominates the system performance and should be designed carefully to match the designed cooling capacity and operation condition. The experimental results also show that the DAAC can work smoothly under various ambient temperatures when the input power of bubble pump is over 200W.

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