scholarly journals Exergy analysis of large temperature difference series air conditioners in subway stations

2020 ◽  
Vol 165 ◽  
pp. 04067
Author(s):  
Kong Xiang jian ◽  
Bi Hai quan ◽  
He Lei
Keyword(s):  
Temperature Difference ◽  
Air Conditioning ◽  
Cooling System ◽  
Water System ◽  
Exergy Efficiency ◽  
Subway Station ◽  
Large Temperature ◽  
Refrigeration System ◽  
Large Temperature Difference ◽  
Difference Series

In view of the large difference in the heat and humidity ratio of each air-conditioning zone in the subway, the unified cooling and dehumidification method is adopted, which changes the traditional connection mode of air-conditioning terminal in parallel. A cooling system of air-conditioning terminal surface cooler in series, i.e. large temperature difference series cooling system, is applied to the subway station. The large temperature difference series cooling system is divided into three subsystems: cooling water system, chilled water system and end refrigeration system. The second law of thermodynamics, namely the law of exergy equilibrium and thermoeconomics, is used to analyze the feasibility and economy of the large temperature difference series system and its subsystems. After comparing energy consumption and economy with the conventional air conditioning system, it was found that the exergy efficiency of the chilled water system using the large temperature difference series cooling system was reduced. However, the exergy efficiency of the end refrigeration system in the subway equipment area has been significantly improved, saving electricity costs, and the investment can be recovered in 3.7 years, and the exergy cost has dropped significantly. The use of a large temperature difference series cooling system in a subway station can achieve the effect of energy saving and cost reduction.

Climatic Effect on the Exergetic Performance of Conventional to Hybrid Evaporative Coolers with Varying Dead State Temperatures in India

2021 ◽  
pp. 1-33
Author(s):  
V Venkateswara Rao ◽  
Santanu Prasad Datta
Keyword(s):  
Air Conditioning ◽  
Sustainability Assessment ◽  
Cooling System ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Direct Expansion ◽  
Dead State ◽  
Evaporative Cooling System ◽  
Expansion Cooling ◽  
Semi Arid

Abstract A comprehensive exergy, exergo-economic and sustainability assessment of seven conventional to hybrid air-conditioning systems comprising direct and indirect evaporative coolers with direct expansion system, and their several combinations integrated into an 8-story domestic building for 5 different cities corresponding to arid, semi-arid, humid sub-tropical, tropical wet and dry, and tropical wet climatic zones across India are investigated based on simulation output from EnergyPlus. The exergetic performances are reported for varying dead state temperatures ranging from 5°C to 40°C while saturated humidity ratio and pressure at system outlet are two other dead state properties. The results reveal that the specific exergy of moist air and exergetic efficiency decrease with increasing dead state temperature and become least at a dead state temperature near to American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) comfort temperature of 23°C. In arid, semi-arid and humid subtropical climates, the three-stage evaporative cooling system exhibited the lowest exergy destruction of 100 J kg−1 and the highest exergy efficiency of 90% at a dead state temperature of 40°C. The two-stage direct evaporative-direct expansion cooling system exhibited superior exergy efficiency of around 90% in tropical wet and dry and tropical wet zones. Further, the Grassmann diagram based on the climate of Hyderabad indicated that the three-stage cooling system is energetically and exergetically optimum with exergy destruction of 28.86%.

Synthesis and characterization of a quaternary copolymer retarder for cementing in a long sealing section with large temperature difference

2020 ◽  
Vol 44 (9) ◽  
pp. 3771-3776
Author(s):  
Zhigang Peng ◽  
Chen Chen ◽  
Qian Feng ◽  
Yong Zheng ◽  
Huan Liu ◽  
...  
Keyword(s):  
Temperature Difference ◽  
Synthesis And Characterization ◽  
Large Temperature ◽  
Temperature Range ◽  
Large Temperature Difference

We synthesized a retarder, which has excellent thickening performance in the temperature range of 90–150 °C.

302 Numerical Analysis of Natural Convection with Large Temperature Difference

2001 ◽  
Vol 2001.54 (0) ◽  
pp. 75-76
Author(s):  
Nobuyuki FUCHIMOTO ◽  
Kazuyoshi MATSUZAKI ◽  
Kazunori KOURA ◽  
Sinya WAKAMIZU ◽  
Hiroaki KURISIMA ◽  
...  
Keyword(s):  
Natural Convection ◽  
Numerical Analysis ◽  
Temperature Difference ◽  
Large Temperature ◽  
Large Temperature Difference

Synthesis and Characterization Performance of a Novel High Temperature Retarder Applied in Long Cementing Interval

2016 ◽  
Vol 847 ◽  
pp. 479-484 ◽  
Author(s):  
Ya Lu ◽  
Ming Li ◽  
Zi Han Guo ◽  
Xiao Yang Guo
Keyword(s):  
Thermal Stability ◽  
Compressive Strength ◽  
High Temperature ◽  
Temperature Difference ◽  
Ph Value ◽  
Rapid Development ◽  
Large Temperature ◽  
Gravimetric Analysis ◽  
Sedimentation Stability ◽  
Large Temperature Difference

In view of the common polymer retarder of AMPS has poor sedimentation stability for slurry in high temperature, and thickening curve for unusual problems, a new terpolymers retarder PSIH which can solve the problem for the large temperature difference was synthesized by free radical aqueous solution copolymerization using styrene sulfonate (SSS), Itaconic acid (IA) and unsaturated hydroxyl ester monomers X . The structure and thermal stability of the copolymer was characterized with gel permeation chromatography (GPC), infrared spectroscopy (IR), and thermal gravimetric analysis (TG). The application performance of the retarder was assessed. The results demonstrated as follows. 1) The preferred synthesis conditions of the retarder is: the mass ratio of SSS/IA/X=9: 3: 1, temperature=60°C, initiator concentration =2%, the reaction time=5h, pH value was controlled in the neutral bias acidity. 2) Synthetic copolymer is the target product with appropriate molecular weight and has good thermal stability with thermal decomposition temperature of the main chain up to 375°C. 3) Compared with ordinary retarder the PSIH has merits as follows: excellent thermal resistant ability and sedimentation stability in high temperature; the rapid development of compressive strength in low temperature, and a big temperature span (30 °C~150 °C). The thickening time of the slurry with 1.0% PSIH is 245 min at 150°C; the compressive strength of cement with the same dosage can get up to 4.7MPa at 30 °C. In short, PSIH has excellent ability to cope with large temperature difference, providing a strong technical support for complex deep well cementing.

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