scholarly journals Performance enhancement of an adsorption chiller by optimum cycle time allocation at different operating conditions

2019 ◽  
Vol 11 (10) ◽  
pp. 168781401988478
Author(s):  
M Gado ◽  
E Elgendy ◽  
Khairy Elsayed ◽  
M Fatouh
Keyword(s):  
Cycle Time ◽  
Time Allocation ◽  
Performance Enhancement ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Enhancement Ratio ◽  
Adsorption Chiller ◽  
Wide Range ◽  
Chilled Water

This article aims to improve the system cooling capacity of an adsorption chiller working with a silica gel/water pair by an allocation of the optimum cycle time at different operating conditions. A mathematical model was established and validated with the literature experimental data to predict the optimum cycle time for a wide range of hot (55°C–95°C), cooling (25°C–40°C), and chilled (10°C–22°C) water inlet temperatures. The optimum and conventional chiller performances are compared at different operating conditions. Enhancement ratio of the system cooling capacity was tripled as the cooling water inlet temperature increased from 25°C to 40°C at constant hot and chilled water inlet temperatures of 85°C and 14°C, respectively. Applying the concept of the optimum cycle time allocation, the system cooling capacity enhancement ratio can reach 15.6% at hot, cooling, and chilled water inlet temperatures of 95°C, 40°C, and 10°C, respectively.

scholarly journals Numerical Simulation of Advanced Adsorption Refrigeration Chiller with Mass Recovery

1970 ◽  
Vol 3 (2) ◽  
pp. 59-67 ◽  
Author(s):  
MZI Khan ◽  
S Sultana ◽  
A Akisawa ◽  
T Kashiwagi
Keyword(s):  
Silica Gel ◽  
Operating Conditions ◽  
Cooling Power ◽  
Inlet Temperature ◽  
Low Grade ◽  
Outlet Temperature ◽  
Adsorption Chiller ◽  
Cycle Simulation ◽  
Chilled Water ◽  
Mass Recovery

This paper investigates the thermodynamic framework of a three-bed advanced adsorption chiller, where the mass recovery scheme has been utilized such that the performances of this chiller could be improved and a CFC-free-based sorption chiller driven by the low-grade waste heat or any renewable energy source can be developed for the next generation of refrigeration. Silica gel-water is chosen as adsorbent-refrigerant pair. The three-bed adsorption chiller comprises with three sorption elements (SEs), one evaporator and one condenser. The configuration of SE1 and SE2 are identical, but the configuration of SE3 is taken as half of SE1 or SE2. Mass recovery process occurs between SE3 with either SE1 or SE2 and no mass recovery between SE1 and SE2 occurs. The mathematical model shown herein is solved numerically. In the present numerical solution, the heat source temperature variation is taken from 50 to 90ºC along with coolant inlet temperature at 30ºC and the chilled water inlet temperature at 14ºC. A cycle simulation computer program is constructed to analyze the influence of operating conditions (hot and cooling water temperature) on COP (coefficient of performance), SCP (specific cooling power), η (chiller efficiency) and chilled water outlet temperature. Keywords: Adsorption; COP; SCP; Mass recovery; Silica gel-waterDOI: 10.3329/jname.v3i2.920 Journal of Naval Architecture and Marine Engineering 3(2006) 59-67 

scholarly journals Development of Waste Heat Fired Activated Carbon Ammonia Adsorption Chiller

2015 ◽  
Vol 11 (2) ◽  
Keyword(s):  
Cycle Time ◽  
Waste Heat ◽  
Operating Conditions ◽  
Cooling Power ◽  
Low Grade ◽  
Outlet Temperature ◽  
Promising Alternative ◽  
Adsorption Chiller ◽  
Wide Range ◽  
Simulated System

Adsorption systems are promising alternative to the existing refrigeration systems in the wake of alarming energy crisis and potential danger due to the use of ozone depleting refrigerants. Sorption systems use thermal energy as its power source and solid adsorbent beds to adsorb and desorb a refrigerant to obtain the desired cooling effect. Solar energy, engine exhaust and low grade waste heat could be used to drive the sorption compressors. The use of non-ozone depleting refrigerant makes these systems environmentally benign. Adsorption refrigeration systems can meet the cooling requirement across a wide range of temperatures. These systems have minimal moving parts and hence they are free of noise, vibration and related problems. This paper will present the description, operation and simulated system characteristics for a 1000W adsorption chiller. The adsorption system performance factors such as coefficient of performance (COP), specific cooling power (SCP), and cycle time were predicted. Parameters such as the generation and adsorption temperature, condenser and evaporator temperature were varied to analyze the influence of the varied operating conditions. A two bed 1000 W capacity adsorption water chiller to chill water from 12 to 7 C was considered for the simulation. COP of the simulated system ranged between 0.3 to 0.4 and SCP from 90 to 180 W/kg AC respectively. The maximum value of cycle time obtained was 25 minutes when the generation outlet temperature was 180 oC.

Experimental Assessment of a Domestic Split Type Air-Conditioner Working with R410A

2016 ◽  
Vol 24 (04) ◽  
pp. 1650021 ◽  
Author(s):  
D. Abd Elraheim ◽  
Osama E. Mahmoud ◽  
M. Fatouh
Keyword(s):  
Volume Flow Rate ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Experimental Results ◽  
Test Facility ◽  
Inlet Temperature ◽  
Air Conditioner ◽  
Humidity Ratio ◽  
Wide Range ◽  
Compressor Power

The objective of the present work is to assess experimentally the performance characteristics of a R410A domestic air conditioner under different in-door operating conditions. In order to achieve this objective, a test facility of the investigated system is developed and experiments are conducted. Experimental results on R410A air conditioning system are obtained over a wide range of in-door operating conditions. Experimental results confirmed that the cooling capacity, compressor power and COP increase by 90.9%, 5.2% and 81.5%, respectively, as air humidity ratio increases from 8 to 25.5[Formula: see text]gw kg[Formula: see text]. The cooling capacity, condenser heat load, compressor power and COP increase by 7.2%, 6.1%, 2.8% and 4.1%, respectively, when the evaporator air inlet temperature increases from 28[Formula: see text]C to 34[Formula: see text]C for a given humidity ratio. COP increases by 25.6% while pressure ratio decreases by 2.5% as the air volume flow rate increases from 400 to 550[Formula: see text]m3 h[Formula: see text].

Heat transfer characteristic modelling and the effect of operating conditions on re-cooled cycle for a scramjet

2011 ◽  
Vol 115 (1164) ◽  
pp. 83-90 ◽  
Author(s):  
W. Bao ◽  
J. Qin ◽  
W. X. Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Transfer Characteristic ◽  
Cooling Capacity ◽  
Sensitivity Study ◽  
Performance Model ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Fuel Flow ◽  
Temperature And Pressure

Abstract A re-cooled cycle has been proposed for a regeneratively cooled scramjet to reduce the hydrogen fuel flow for cooling. Upon the completion of the first cooling, fuel can be used for secondary cooling by transferring the enthalpy from fuel to work. Fuel heat sink (cooling capacity) is thus repeatedly used and fuel heat sink is indirectly increased. Instead of carrying excess fuel for cooling or seeking for any new coolant, the cooling fuel flow is reduced, and fuel onboard is adequate to satisfy the cooling requirement for the whole hypersonic vehicle. A performance model considering flow and heat transfer is build. A model sensitivity study of inlet temperature and pressure reveals that, for given exterior heating condition and cooling panel size, fuel heat sink can be obviously increased at moderate inlet temperature and pressure. Simultaneously the low-temperature heat transfer deterioration and Mach number constrains can also be avoided.

Experimental Investigation of a Pilot Compression Chiller With Alternatives Refrigerants R401a and R134a

2005 ◽  
Author(s):  
M. Fatouh
Keyword(s):  
Experimental Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Water Mass ◽  
Cooling Water ◽  
Cooling Capacity ◽  
Inlet Temperature ◽  
Chilled Water ◽  
Water Mass Flow Rate

This paper reports the results of an experimental investigation on a pilot compression chiller (4 kW cooling capacity) working with R401a and R134a as R12 alternatives. Experiments are conducted on a single-stage vapor compression refrigeration system using water as a secondary working fluid through both evaporator and condenser. Influences of cooling water mass flow rate (170–1900 kg/h), cooling water inlet temperature (27–43°C) and chilled water mass flow rate (240–1150 kg/h) on performance characteristics of chillers are evaluated for R401a, R134a and R12. Increasing cooling water mass flow rate or decreasing its inlet temperature causes the operating pressures and electric input power to reduce while the cooling capacity and coefficient of performance (COP) to increase. Pressure ratio is inversely proportional while actual loads and COP are directly proportional to chilled water mass flow rate. The effect of cooling water inlet temperature, on the system performance, is more significant than the effects of cooling and chilled water mass flow rates. Comparison between R12, R134a and R401a under identical operating conditions revealed that R401a can be used as a drop-in refrigerant to replace R12 in water-cooled chillers.

Mechanical Design and Testing of a 2.5 MW sCO2 Compressor Loop

2021 ◽  
Author(s):  
Stefan D. Cich ◽  
J. Jeffrey Moore ◽  
Chris Kulhanek ◽  
Meera Day Towler ◽  
Jason Mortzheim
Keyword(s):  
High Efficiency ◽  
Mechanical Design ◽  
Guide Vane ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Inlet Temperature ◽  
Design Changes ◽  
Wide Range ◽  
Inlet Conditions ◽  
Design And Testing

Abstract An enabling technology for a successful deployment of the sCO2 close-loop recompression Brayton cycle is the development of a compressor that can maintain high efficiency for a wide range of inlet conditions due to large variation in properties of CO2 operating near its dome. One solution is to develop an internal actuated variable Inlet Guide Vane (IGV) system that can maintain high efficiency in the main and re-compressor with varying inlet temperature. A compressor for this system has recently been manufactured and tested at various operating conditions to determine its compression efficiency. This compressor was developed with funding from the US DOE Apollo program and industry partners. This paper will focus on the design and testing of the main compressor operating near the CO2 dome. It will look at design challenges that went into some of the decisions for rotor and case construction and how that can affect the mechanical and aerodynamic performance of the compressor. This paper will also go into results from testing at the various operating conditions and how the change in density of CO2 affected rotordynamics and overall performance of the machine. Results will be compared to expected performance and how design changes were implanted to properly counter challenges during testing.

scholarly journals Design of a Wide-Range Centrifugal Compressor Stage for Supercritical CO2 Power Cycles

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Robert Pelton ◽  
Sewoong Jung ◽  
Tim Allison ◽  
Natalie Smith
Keyword(s):  
Operating Conditions ◽  
Low Flow ◽  
Inlet Temperature ◽  
Compressor Stage ◽  
Stage Design ◽  
Power Cycles ◽  
Design Point ◽  
Operating Range ◽  
Wide Range ◽  
Compressor Efficiency

Supercritical carbon dioxide (sCO2) power cycles require high compressor efficiency at both the design point and over a wide operating range. Increasing the compressor efficiency and range helps maximize the power output of the cycle and allows operation over a broader range of transient and part-load operating conditions. For sCO2 cycles operating with compressor inlets near the critical point, large variations in fluid properties are possible with small changes in temperature or pressure. This leads to particular challenges for air-cooled cycles where compressor inlet temperature and associated fluid density are subject to daily and seasonal variations as well as transient events. Design and off-design operating requirements for a wide-range compressor impeller are presented where the impeller is implemented on an integrally geared compressor–expander concept for a high temperature sCO2 recompression cycle. In order to satisfy the range and efficiency requirements of the cycle, a novel compressor stage design incorporating a semi-open impeller concept with a passive recirculating casing treatment is presented that mitigates inducer stall and extends the low flow operating range. The stage design also incorporates splitter blades and a vaneless diffuser to maximize efficiency and operating range. These advanced impeller design features are enabled through the use of direct metal laser sintering (DMLS) manufacturing. The resulting design increases the range from 45% to 73% relative to a conventional closed impeller design while maintaining high design point efficiency.

The performance of a centrifugal compressor with a tandem impeller in off-design conditions

2019 ◽  
Vol 234 (2) ◽  
pp. 156-172 ◽  
Author(s):  
Ziliang Li ◽  
Xingen Lu ◽  
Ge Han ◽  
Yanfeng Zhang ◽  
Shengfeng Zhao ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Performance Enhancement ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Complex Flow ◽  
Maximum Enhancement ◽  
Operating Range ◽  
Wide Range ◽  
Compressor Performance ◽  
Low Efficiency

Centrifugal compressors often suffer relatively low efficiency and a terrible operating range particularly due to the complex flow structure and intense impeller/diffuser interaction. Numerous studies have focused on improving the centrifugal compressor performance using many innovative ideas, such as the tandem impeller, which has become increasingly attractive due to its ability to achieve the flow control with no additional air supply configurations and control costs in compressor. However, few studies that attempted to the investigation of tandem impeller have been published until now and the results are always contradictory. To explore the potential of the tandem impeller to enhance the compressor performance and the underlying mechanism of the flow phenomena in the tandem impellers, this paper numerically investigated a high-pressure-ratio centrifugal compressor with several tandem impellers at off-design operating speeds. The results encouragingly demonstrate that the tandem impeller can achieve a performance enhancement over a wide range of operating conditions. Approximately 1.8% maximum enhancement in isentropic efficiency and 5.0% maximum enhancement in operating range are achieved with the inducer/exducer circumferential displacement of [Formula: see text] = 25% and 50%, respectively. The observed stage performance gain of the tandem impellers decreases when the operating speed increases due to the increased inducer shock, increased wake losses, and deteriorated tandem impeller discharge flow uniformity. In addition, the tandem impeller can extend the impeller operating range particularly at low rotation speeds, which is found to be a result from the suppression of the low-momentum fluid radial movement. The results also indicate that the maximum flux capacity of the tandem impeller decreases due to the restriction of the inducer airfoil Kutta–Joukowsky condition.

Improved Gas Turbine Efficiency Through Alternative Regenerator Configuration

2002 ◽  
Author(s):  
Paul A. Dellenback
Keyword(s):  
Gas Turbine ◽  
Operating Conditions ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Optimum Pressure ◽  
Model Calculations ◽  
Turbine Engine ◽  
Combustion Gases ◽  
Wide Range ◽  
Temperature Combustion

An alternative configuration for a regenerative gas turbine engine cycle is presented that yields higher cycle efficiencies than either simple or conventional regenerative cycles operating under the same conditions. The essence of the scheme is to preheat compressor discharge air with high temperature combustion gases before the latter are fully expanded across the turbine. The efficiency is improved because air enters the combustor at a higher temperature, and hence heat addition in the combustor occurs at a higher average temperature. The heat exchanger operating conditions are more demanding than for a conventional regeneration configuration, but well within the capability of modern heat exchangers. Models of cycle performance exhibit several percentage points of improvement relative to either simple cycles or conventional regeneration schemes. The peak efficiencies of the alternative regeneration configuration occur at optimum pressure ratios that are significantly lower than those required for the simple cycle. For example, at a turbine inlet temperature of 1300°C (2370°F), the alternative regeneration scheme results in cycle efficiencies of 50% for overall pressure ratios of 22, whereas simple cycles operating at the same temperature would yield efficiencies of only 43.8% at optimum pressure ratios of 50, which are not feasible with current compressor designs. Model calculations for a wide range of parameters are presented, as are comparisons with simple and conventional regeneration cycles.

Heat exchanger design optimization for mitigation of diesel engine exhaust fouling

2020 ◽  
pp. 1-36
Author(s):  
Victor C. Aiello ◽  
Girish Kini ◽  
Marcel Staedter ◽  
Srinivas Garimella
Keyword(s):  
Design Optimization ◽  
Heat Pump ◽  
Waste Heat ◽  
Large Data ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Component Level ◽  
Pressure Drops ◽  
Single Tube ◽  
Wide Range

Abstract The design optimization of a diesel exhaust coupled heat and mass exchanger that drives a 2.71 kW cooling capacity absorption heat pump is presented in this study. Fouling layer thermal resistance and pressure drops from single-tube experiments are used to develop a thermodynamic, heat transfer, and pressure drop model for the exhaust coupled desorber. A parametric study is performed to select a desorber design that meets system performance while minimizing footprint. Experimental heat duties and pressure drops are within 10% and 3%, respectively, of the model predictions. Thus, large data sets from single-tube experiments with representative geometries are successful in accounting for fouling effects at the component level. Desorber design optimization based on this approach ensures continued heat pump performance after fouling. This study, along with the single tube experiments, presents a systematic approach to design exhaust-coupled heat exchangers while considering the effects of fouling. These results are applicable for a wide range of waste-heat recovery applications and this method can be extended to different geometries and operating conditions.

Sign in / Sign up

Export Citation Format

Share Document