Effect of the Thermostatic Expansion Valve Characteristics on the Stability of a Refrigeration System: Part II

2003 ◽  
Author(s):  
Amit Kulkarni ◽  
Dereje Agonafer ◽  
Roger Schmidt
Keyword(s):  
Load Condition ◽  
Transient Behavior ◽  
System Stability ◽  
Stable Operation ◽  
Refrigeration System ◽  
Expansion Valve ◽  
System Part ◽  
Suction Line ◽  
The Stability ◽  
Experimental Bench

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. The challenge has been to limit the rise in chip temperature. In the past virtually all-commercial computers were designed to operate at temperatures above the ambient. However researchers have identified the advantages of operating electronics at low temperatures. The current research focuses on IBM’s mainframe, which uses a conventional refrigeration system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. An experimental bench was built to study the effect of variation of evaporator outlet superheat on system performance. Three different types of thermostatic expansion valves were tested in order to verify that the bulb size and bulb location have significant effect on the transient behavior of the system. Bulbs of each of the three thermostatic expansion valves were mounted at five different locations on the suction line. It was observed that the overall system stability increases as we move closer to the evaporator exit. It was also observed that there exists a region in the suction line at which the superheat variation is the least and placing the bulb at this region gives maximum stable operation of the system. This region can be defined as the minimum stable superheat point. Tests were conducted at five different load conditions 1000W, 750W, 500W, 250W and no load condition. It was observed that the system was the most stable at full load condition for all three types of valves and system stability consistently decreased as the load was decreased.

Effect of the Location and the Properties of Thermostatic Expansion Valve Sensor Bulb on the Stability of a Refrigeration System

2005 ◽  
Vol 127 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Veerendra Mulay ◽  
Amit Kulkarni ◽  
Dereje Agonafer ◽  
Roger Schmidt
Keyword(s):  
Low Temperature ◽  
Thermal Resistance ◽  
Time Constant ◽  
Thermophysical Properties ◽  
System Performance ◽  
System Stability ◽  
System Response ◽  
Refrigeration System ◽  
Expansion Valve ◽  
The Stability

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. The challenge has been to limit the rise in chip temperature. In the past, virtually all commercial computers were designed to operate at temperatures above the ambient. However, researchers have identified the advantages of operating electronics at low temperatures. The primary purpose of low-temperature cooling using a vapor compression system are faster switching times of semiconductor devices, increased circuit speed due to lower electrical resistance of interconnecting materials, and a reduction in thermally induced failures of devices and components. Achievable performance improvements range from 1% to 3% for every 10°C lower transistor temperature, depending on the doping characteristics of the chip. The current research focuses on IBM’s mainframe, which uses a conventional refrigeration system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. Although performance has been the key driver in the use of this technology, the second major reason for designing a system with low-temperature cooling is the improvement achieved in reliability to counteract detrimental effects, which rise as technology is pushed to the extremes. A mathematical model is developed to determine the time constant for an expansion valve sensor bulb. This time constant varies with variation in the thermophysical properties of the sensor element; that is, bulb size and bulb liquid. An experimental bench is built to study the effect of variation of evaporator outlet superheat on system performance. The heat load is varied from no load to full load (1 KW) to find out the system response at various loads. Experimental investigation is also done to see how the changes in thermophysical properties of the liquid in the sensor bulb of the expansion valve affect the overall system performance. Different types of thermostatic expansion valves are tested to investigate that bulb size, bulb constant, and bulb location have significant effects on the behavior of the system. Thermal resistance between the bulb and evaporator return line can considerably affect the system stability, and by increasing the thermal resistance, the stability can be further increased.

Effect of the Thermostatic Expansion Valve Characteristics on the Stability of a Refrigeration System

2003 ◽  
Author(s):  
Veerendra Mulay ◽  
Dereje Agonafer ◽  
Roger Schmidt
Keyword(s):  
Low Temperature ◽  
Thermal Resistance ◽  
Physical Properties ◽  
Time Constant ◽  
System Performance ◽  
System Stability ◽  
Refrigeration System ◽  
Expansion Valve ◽  
The Stability ◽  
Thermo Physical Properties

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. The challenge has been to limit the rise in chip temperature. In the past virtually all-commercial computers were designed to operate at temperatures above the ambient. However researchers have identified the advantages of operating electronics at low temperatures. The primary purpose of low temperature cooling using vapor compression system are faster switching times of semiconductor devices, increased circuit speed due to lower electrical resistance of interconnecting materials, and a reduction in thermally induced failures of devices and components. Achievable performance improvements range from 1 to 3% for every 10°C lower transistor temperature, depending on the doping characteristics of the chip. The current research focuses on IBM’s mainframe, which uses a conventional refrigeration system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. Although performance has been the key driver in the use of this technology, the second major reason for designing a system with low temperature cooling is the improvement achieved in reliability to counteract detrimental effects, which rise as technology is pushed to the extremes. A mathematical model is developed to determine the time constant for expansion valve sensor blub. This time constant varies with variation in thermo-physical properties of sensor element that is bulb size and blub liquid. An experimental bench is built to study the effect of variation of evaporator outlet superheat on system performance. The heat load is varied from no load to full load (1KW) to find out the system response at various loads. Experimental investigation is also done to see how the changes in thermo-physical properties of the liquid in sensor bulb of expansion valve affect the overall system performance. Different types of thermostatic expansion valves are tested to investigate that bulb size; bulb constant and bulb location have significant effect on the behavior of the system. Thermal resistance between the bulb and evaporator return line can considerably affect the system stability and by increasing the thermal resistance, the stability can be further increased.

Summary of the Stability Chanllenges and Safe Operation of Power Systems in View of Dispatching

2014 ◽  
Vol 960-961 ◽  
pp. 1588-1591
Author(s):  
Xiang Dong Zhao ◽  
Xin Zhao ◽  
Ming Jun Lv ◽  
Jian Guo Liu ◽  
Feng Zhen Liu ◽  
...  
Keyword(s):  
Power Systems ◽  
Power System ◽  
Rapid Development ◽  
Power Grids ◽  
System Stability ◽  
Stable Operation ◽  
Safe Operation ◽  
The Stability ◽  
Continuous Power ◽  
Grid Market

The Internet and the gradual implementation of the continuous power grid market in recent years make the power system more complex under different operating environment. Safe and stable operation of power grids have become increasingly important . With the rapidf development of the grid and constant innovation, safe and stable operation also has a new requirement , because the rapid development of the power system brings more This paper analyzes the causes of blackouts and reviews security of the power system stability problems related to measures on the security and stability of the power system operation .

Impact of Area Contact Between Sensor Bulb and Evaporator Return Line on Modular Refrigeration Unit: Computational and Experimental

2005 ◽  
Vol 127 (1) ◽  
pp. 95-100 ◽  
Author(s):  
Saket Karajgikar ◽  
Nikhil Lakhkar ◽  
Dereje Agonafer ◽  
Roger Schmidt
Keyword(s):  
Mechanical Analysis ◽  
Evaporator Temperature ◽  
Thermally Induced ◽  
The Past ◽  
Refrigeration Unit ◽  
Expansion Valve ◽  
Flow Through ◽  
The Stability ◽  
Experimental Bench ◽  
Server System

In the past, virtually all commercial computers were designed to operate at temperatures above the ambient and were primarily air-cooled. However, researchers have always known the advantages of operating electronics at low temperatures. This facilitates faster switching time of semiconductor devices, increased circuit speeds due to lower electrical resistance of interconnecting materials, and reduction in thermally induced failures of devices and components. Depending on the doping characteristics of the chip, performance improvement ranges from 1% to 3% for every 10°C lower transistor temperature can be realized. The IBM S/390 high-end server system is the first IBM design which uses a conventional refrigeration system to maintain the chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperature. In previous work, the focus was to study the effect of variation of evaporator outlet superheat on the flow through thermostatic expansion valve at varying evaporator temperature. The effect of change in bulb location and effect of bulb time constant on the hunting at the evaporator has been reported. The effect of area contact on the stability of the system is been predicted theoretically. Mechanical analysis is performed in order to check the stresses induced. The evaporator return line and the sensor bulb are simply attached. The effect of area contact is further studied experimentally on an experimental bench.

scholarly journals Modelling and Simulation of a Retail Commercial Refrigeration System

2021 ◽  
pp. 1-27
Author(s):  
Oliver Brownbridge ◽  
Matthew Sully ◽  
Joshua Noons ◽  
Ibrahim Albayati
Keyword(s):  
Research Centre ◽  
Refrigeration System ◽  
Total Energy Consumption ◽  
Holistic View ◽  
Expansion Valve ◽  
Suction Line ◽  
Valve Opening ◽  
The Uk ◽  
High Level ◽  
The University

Abstract Commercial food outlets in the UK are responsible for 3% of the UK total energy consumption, with refrigeration systems account for 29% of this total. This highlights the potential and importance of huge energy saving within commercial refrigeration systems. In this paper, a validated model that simulates a commercial refrigeration system installed over 2000 sqft to mimic a real express store installed at Riseholme Refrigeration Research Centre at the University of Lincoln, UK, is developed and presented. The detailed modelling of the display case using a temperature model comprising of three states include air inside the display case, products, and the evaporator. Additionally, the model presents a holistic view of the whole system with each subsystem cohesively linked together. Further focus has been given on the high temperature (HT) system due to the high level of installations of this system found in retail commercial refrigeration stores as well as low temperature (LT) systems featuring doors which decrease the heat transfer from the store into the cases. It is concluded that the trends of the simulation results for the display case temperatures, expansion valve opening degree, suction line pressures, and compressors power consumption, all have high resemblance to the trends of collected data obtained from Riseholme Refrigeration Research Centre. This supports the validation of the developed model.

To Improve the Performance and Efficiency of Refrigeration Systems by Using Refrigerant Pumps

2013 ◽  
Vol 385-386 ◽  
pp. 233-236
Author(s):  
Qing Jiang Liu ◽  
Zeng Zhi Yuan ◽  
Jin Ting Sun ◽  
Fang Han
Keyword(s):  
Pressure Difference ◽  
System Performance ◽  
Low Pressure ◽  
System Stability ◽  
Refrigeration System ◽  
Expansion Valve

In order to improve refrigeration system stability and efficiency of the low pressure difference between thermostatic expansion valve, it is researched that the refrigeration system is the refrigerate capacity of the HSN7471-75 compressors. The system performance is analyzed and compared in the case of with and without refrigerant pumps. The results indicate that the COP of the refrigeration system with a pump can increase 31%. The reliability of system is also improved.

scholarly journals Análisis de la generación de las irreversibilidades a partir del Coeficiente de Operación en un sistema de refrigeración por compresión mecánica de vapor con R-134a

2019 ◽  
pp. 10-15
Author(s):  
Carlos Rangel-Romero ◽  
Juan Carlos Rojas-Garnica ◽  
Guillermo Flores-Martínez ◽  
Antonio Barcelata-Pinzón
Keyword(s):  
Vapor Compression ◽  
Refrigeration System ◽  
Pressure Drops ◽  
Liquid Line ◽  
Expansion Valve ◽  
Individual Contributions ◽  
Suction Line ◽  
Vapor Compression Refrigeration ◽  
R 134A ◽  
Mathematical Process

This paper presents the development of individual contributions, in the generation of irreversibilities, of a refrigeration system based on the Coefficient of Operation (COP). The generation of irreversibilities has been widely analyzed using the principles of the first and second laws of thermodynamics. This analysis uses the parameters of enthalpy, entropy as well as the temperature and heat generated in each component. The method proposed in this work improves the accuracy of the calculations due to the use of the COP in the mathematical process, which includes the processes of heat transfer and pressure drops developed in the evaporator, suction line, compressor, discharge line, condenser, liquid line and expansion valve of the mechanical vapor compression refrigeration system. The mathematical analyzes and the experimental results are shown, with these it is concluded that the exposed procedure is closer to the real conditions than those traditional procedures found in the text books.

scholarly journals Analyzing the Impact of Loop Parameter Variations on the Transient Response of Second Order Voltage-Switched CP-PLL

2021 ◽  
Vol 11 (1) ◽  
pp. 6687-6690
Author(s):  
E. Ali ◽  
D. Narwani ◽  
A. M. Bughio ◽  
N. Nizamani ◽  
S. H. Siyal ◽  
...  
Keyword(s):  
Transient Response ◽  
Transient Behavior ◽  
Phase Locked Loop ◽  
Stable Operation ◽  
Loop Filter ◽  
Mixed Signal ◽  
Target Frequency ◽  
Parameter Variations ◽  
The Stability ◽  
The Impact

The analysis of the behavior of Charge Pump Phase-Locked Loop (CP-PLL) is a challenging task due to its mixed-signal architecture. Out of its two types, i.e. Current Switched CP-PLL (CSCP-PLL) and Voltage Switched CP-PLL (VSCP-PLL), the prior produces symmetrical pump currents, resulting in an appropriate transient performance to be analyzed. The loop parameters are important to set the gain, target frequency, and assure the stability of the system. The more important is the bandwidth of the loop, which is dependent on the loop filter parameters to perform stable operation and locking time. In this paper, the impact of loop parameter variations on the overall transient behavior of the system is investigated. It has been shown that loop parameters play an important role to ease the design of mixed-signal PLLs.

scholarly journals A REVIEW OF THE EFFECTS OF CHANGES IN THE VOID FRACTION OF THE SUPERHEATED REGION ON THE TEV OPERATION AND EVAPORATOR STABILITY

2016 ◽  
Vol 15 (2) ◽  
pp. 38
Author(s):  
R. A. Ramos ◽  
J. Castro
Keyword(s):  
Literature Review ◽  
Void Fraction ◽  
Vapor Compression ◽  
The Third ◽  
Lubricant Oil ◽  
Expansion Valve ◽  
Suction Line ◽  
Vapor Compression Refrigeration ◽  
The Stability ◽  
Proper Operation

A level of superheat is necessary to ensure proper operation of vapor- compression refrigeration systems. An overly superheated vapor prior to entering the compressor can render the system inefficient, while inadequate superheat can result in evaporator instability and compressor damage. The void fraction present in the suction line is directly related to evaporator stability and the hunting phenomenon in the thermostatic expansion valve (TEV). This article aims at reviewing superheated region-related researches in the field of refrigeration as they relate to the operation of the TEV and the stability of the evaporator. In a first part, literature review will explain the causes of the void fraction in the superheated region and the second part describes the effects of the lubricant oil on the void fraction. The third part of this article is a review of the effects of the superheated region on the TEV and on evaporator stability, explaining the causes of the hunting phenomena and evaporator instability.

Sign in / Sign up

Export Citation Format

Share Document