600 MW Direct Air-Cooling Unit Back-Pressure Optimization and Theoretical Analysis

2014 ◽  
Vol 875-877 ◽  
pp. 1739-1743
Author(s):  
Hong Bin Zhao ◽  
Yong Hui Yan ◽  
Meng Li
Keyword(s):  
Efficiency Analysis ◽  
Exergy Efficiency ◽  
Back Pressure ◽  
Exergy Loss ◽  
Air Cooling ◽  
Power Gain ◽  
Cooling Unit ◽  
Before And After ◽  
Actual Operation ◽  
Fan Speed

In recent years, direct air cooling units have developed rapidly in China, but in the actual operation, the back-pressure often deviate from the optimal back-pressure, which affect the economy of the unit. The paper has figured out the optimum back-pressure, fan speed and power gain with the method of equivalent enthalpy drop; the paper also worked out the exergy loss of each device before and after the optimization. Through the exergy efficiency analysis of the devices before and after the optimization, we find out that after optimization, exergy loss of the turbine reduces by 0.954MW and the net amount of the generated power increases 130.5kW, the net exergy efficiency of units improves about 0.018 percent points.

Heat Power Determination of Dv-290 Refrigerator’s Evaporator on the Basis of Thermodynamic Parameters of Inlet Air / Określenie Mocy Cieplnej Parownika Chłodziarki Dv-290 Na Podstawie Parametrów Termodynamicznych Powietrza Wlotowego

2012 ◽  
Vol 57 (4) ◽  
pp. 911-920
Author(s):  
Bernard Nowak ◽  
Zbigniew Kuczera
Keyword(s):  
Thermodynamic Parameters ◽  
Thermal Power ◽  
Correlation Coefficients ◽  
Specific Humidity ◽  
Physical Parameters ◽  
Air Cooling ◽  
Regression Equations ◽  
Evaporation And Condensation ◽  
Before And After ◽  
The Given

Abstract The present paper introduces a method for calculating the thermal power of DV-290 mining air cooler’s evaporator. The power usually differs from the nominal power given by the manufacturer. The thermodynamic parameters of cooled air are not obtained as a result of in situ measurements, but in indirect manner that is by determining the evaporation and condensation’s pressure values of R407C refrigerant. The pressure dependencies formulated as a function of air enthalpy at the evaporator’s inlet were obtained using calculations of a computer program which solves the system of equations describing heat and mass transfer in the refrigerator’s compressor on the basis of previous measurements of air performed before and after its cooling. The obtained dependencies are demonstrated in a graphical (fig. 2 and fig. 3) and analytical (the regression equations (19) and (20)) manner, the values of correlation coefficients are also presented. For the known evaporation and condensation pressure values of the refrigerant, and thus for its basic physical parameters the complete thermal power of the evaporator was determined, that is its: air cooling overt power, dehumidification occult power, temperature, relative humidity and specific humidity of air after its cooling. In addition, using the mentioned method, the capacity of DV-290 refrigerator’s evaporator is provided for the given thermodynamic parameters of air before cooling, along with air thermodynamic parameters after cooling.

Energy and exergy analysis of a downstream single-row air washer at different droplet diameters for air cooling application

2022 ◽  
pp. 095440622110645
Author(s):  
Minhua Huang ◽  
Haiqiao Wang ◽  
Feng Tian ◽  
Junxin Huang ◽  
Shiqiang Chen ◽  
...  
Keyword(s):  
Performance Indicator ◽  
Droplet Diameter ◽  
Exergy Efficiency ◽  
Air Cooling ◽  
Design Calculation ◽  
Outlet Temperature ◽  
Single Row ◽  
Energy And Exergy ◽  
Water Gas ◽  
Gas Ratio

This study proposes a downstream single-row air washer for air cooling. The theoretical energy and exergy balance models were established at different droplet diameters and verified by the experimental data. Based on the abovementioned theoretical relationship, the single performance indicator of heat exchange efficiency (HEE) and exergy efficiency was quantitatively analyzed; a comprehensive analysis method of two indicators was proposed, combining HEE and exergy efficiency, and a numerical simulation was carried out. Results show that the smaller the droplet diameter and the larger the water–air ratio, the lower the dry-bulb temperature of the outlet air and the higher the HEE and exergy flux destruction. When the droplet diameter is less than 440 μm, the droplet diameter does not affect exergy efficiency and dry-bulb temperature. When the droplet diameter is larger than 440 μm, the droplet diameter is positively correlated with the air outlet dry-bulb temperature and exergy efficiency; in contrast, the water–gas ratio is negatively correlated with the air outlet dry-bulb temperature. An engineering case reveals that when the air outlet temperature is less than 34°C, the critical water–gas ratio can be set as 2.6 (mass ratio). At this time, the HEE is more than 90%, the exergy efficiency is more than 60%, and the critical value of droplet diameter is 440 μm. The research results provide an essential theoretical basis for the optimization of engineering design calculation.

scholarly journals Exergy Analysis of Polymer Electrolyte Fuel Cell Systems Using Methanol

2003 ◽  
Author(s):  
Akimitsu Ishihara ◽  
Shigenori Mitsushima ◽  
Nobuyuki Kamiya ◽  
Ken-Ichiro Ota
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Steam Reforming ◽  
Waste Heat ◽  
Material Balance ◽  
Cell Voltage ◽  
Exergy Efficiency ◽  
Exergy Loss ◽  
Polymer Electrolyte Fuel Cell ◽  
The Difference

An exergy (available energy) analysis has been conducted on a typical polymer electrolyte fuel cell (PEFC) system using methanol. The material balance and enthalpy balance were calculated for the PEFC system using methanol steam reforming, and the exergy flow was obtained. Based on these results, the exergy loss in each unit was obtained, and the difference between the enthalpy and exergy was discussed. The exergy loss in this system was calculated to be 178kJ/mole MeOH for the steam reforming process of methanol. Although the enthalpy efficiency approached unity as the recovery rate of the waste heat from the cell approached unity, the exergy efficiency remained around 0.45 since the cell’s operating temperature of 80°C is low. It was also found that the cell voltage should exceed 0.82V in order to obtain the exergy efficiency of 0.5 or higher. A direct methanol fuel cell (DMFC) was analyzed using the exergy and compared with the methanol reforming PEFC. In order to obtain the exergy efficiency higher than that of PEFC with steam reforming, the cell voltage of the DMFC should be 0.48V or greater at the current density of 600mA/cm2.

scholarly journals INTENSIFICATION OF HEAT TRANSFER IN TUBES WITH FLUIDIZED LAYER

2020 ◽  
Vol 2018 (1) ◽  
pp. 12-12
Author(s):  
Kirill Zaharov ◽  
Aleksey Bal'chugov
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Air Cooling ◽  
Fluidized Layer ◽  
Cooling Unit

It is shown that one of the promising methods of heat exchange intensification in the air-cooling unit is the organization of a fluidized layer.

scholarly journals Improving the performance of the air-cooling unit in the cooling system of a radar

2021 ◽  
Vol 2057 (1) ◽  
pp. 012004
Author(s):  
Yu A Borisov ◽  
V V Volkov-Muzilev ◽  
D A Kalashnikov ◽  
H S Khalife
Keyword(s):  
Heat Exchanger ◽  
Gas Flow ◽  
Cooling System ◽  
Experimental Studies ◽  
Air Cooling ◽  
Axial Fan ◽  
Gas Dynamic ◽  
Cooling Unit ◽  
Calculation Results ◽  
Axial Fans

Abstract The article discusses the issues of reducing the size of the cooling unit of the antenna of a radar station by improving the gas-dynamic processes occurring in the air-cooling unit. The results of the experimental studies of the gas flow in a plate-fin heat exchanger, being blown by one axial fan are presented. The feasibility of changing the number of axial fans for organizing a more uniform flow around the heat-exchange surfaces has been determined by calculation and theoretical methods. The calculation results are confirmed by experimental studies of the air flow in the segment of the heat exchanger, which is provided by a smaller fan.

scholarly journals Efficiency Analysis of Microfinance Institutions in Bangladesh: Does Regulation Matter?

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Farhana Ferdousi
Keyword(s):  
Efficiency Analysis ◽  
Malmquist Productivity Index ◽  
Productivity Index ◽  
Data Envelopment ◽  
Microfinance Institutions ◽  
Tobit Regression ◽  
Productivity Increase ◽  
Before And After ◽  
Tools And Techniques ◽  
Productive Growth

The aim of this study is to measure efficiency of various Microfinance Institutions (MFIs) in Bangladesh before and after introducing Microcredit Regulatory Authority (MRA) in order to capture the immediate impact of regulation. Data Envelopment Analysis (DEA) and Malmquist Productivity index technique have been used for this study. Findings reveal that 35% firms’ average productivity increase sharply after enacting microfinance regulation. Seven firms have been graduated from the inefficiency level to efficiency level. However, most of the firms among the increased efficiency list are comparatively young in terms of starting their microfinance operations. Result of Tobit regression does not find any significant relationship between efficiency and regulation. Due to regulation, only number of outreach increases but to ensure more productive growth, MRA needs to be more proactive in strengthening policy environment and educating MFIs to be better equipped with sound financial and managerial tools and techniques.

Sign in / Sign up

Export Citation Format

Share Document