Capillary Tube as an Expansion Device in a CO2 (R744) Transcritical Heat Pump System

2015 ◽  
pp. 360-377
Author(s):  
Neeraj Agrawal ◽  
Souvik Bhattacharyya
Keyword(s):  
Critical Temperature ◽  
Heat Pump ◽  
Capillary Tube ◽  
Optimum Operating ◽  
Optimal Length ◽  
Pump System ◽  
Optimum Operating Condition ◽  
Heat Pump System ◽  
Expansion Valve ◽  
Vapour Compression

Natural refrigerants which are ecologically safe and were in use extensively in the pre-CFC era are witnessing a revival of CO2 (R744). Inherently being a low critical temperature (31.2 ?C) refrigerant, the CO2 cycle based system operates in transcritical mode offers an opportunity to obtain an optimum operating condition. Capillary tubes which are extensively used in small size vapour compression systems work very differently in a CO2 transcritical heat pump system. In this chapter it is described that installation of a capillary tube having an appropriately designed length replacing an expansion valve will result in a natural adjustment of the gas cooler pressure, so that the system balance always shifts to a favourable COP direction; this is contrary to the scepticism that exists on the capability of a capillary tube to attain the optimal pressure operation. There is an optimal length of capillary tube for a given diameter at which the heat pump runs optimally.

scholarly journals Simulation on vapour compression heat pump system for rough rice drying

2020 ◽  
Vol 542 ◽  
pp. 012042
Author(s):  
L O Nelwan ◽  
R P A Setiawan ◽  
M Yulianto ◽  
Irfandi ◽  
M Fachry ◽  
...  
Keyword(s):  
Heat Pump ◽  
Pump System ◽  
Heat Pump System ◽  
Rough Rice ◽  
Rice Drying ◽  
Vapour Compression

scholarly journals Electronically Controlled Expansion Valve for Use in a Geothermal Heat Pump System

2014 ◽  
Vol 7 (1) ◽  
Author(s):  
H. I. Abu Mulaweh ◽  
D. W Mueller ◽  
H Oloomi
Keyword(s):  
Fuzzy Control ◽  
Heat Pump ◽  
Control Algorithm ◽  
Geothermal Heat ◽  
Pump System ◽  
Heat Pump System ◽  
Geothermal Heat Pump ◽  
Expansion Valve ◽  
Sensor Configuration ◽  
Fuzzy Control Algorithm

This paper presents a detailed design of a development control board that can control an electronic expansion valve in a geothermal heat pump. The design utilized a microcontroller based system with a fuzzy control algorithm, and a temperature and pressure sensor configuration at the inlet of the compressor. The fuzzy control was designed and simulated using Simulink in Matlab. The control algorithm takes the information that the microcontroller obtained from the pressure and temperature sensor and adjusts the valve accordingly to control the amount of superheat. The controller was able to bring the superheat to the desired set point of 10°F ±2°F and maintain it.

OS4-06 Study of the CO2-Heat Pump System Using Capillary Tube : Part 1 Steady State Characteristics of the Capillary Tube

2005 ◽  
Vol 2005.10 (0) ◽  
pp. 173-174
Author(s):  
Kazuki HARAGUCHI ◽  
Keisuke TAKAYAMA ◽  
Yoshiharu AMANO ◽  
Takumi HASHIZUME ◽  
Michio SASAKI
Keyword(s):  
Steady State ◽  
Heat Pump ◽  
Capillary Tube ◽  
Pump System ◽  
Heat Pump System

Surge Onset in Turbo Heat Pumps

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Jieun Song ◽  
Jung Chan Park ◽  
Kil Young Kim ◽  
Jinhee Jeong ◽  
Seung Jin Song
Keyword(s):  
Heat Pump ◽  
Heat Exchangers ◽  
Heat Pumps ◽  
Working Fluid ◽  
Pump System ◽  
Heat Pump System ◽  
Linearized Stability ◽  
Stability Model ◽  
Expansion Valve ◽  
Mass Spring

A typical turbo heat pump system consists of a centrifugal compressor, expansion valve, and two heat exchangers—a condenser and evaporator. Compared to a gas turbine, a turbo heat pump introduces additional complexities because it is a two-phase closed-loop system with heat exchange using a real gas/liquid (refrigerant) as the working fluid. For the first time, surge onset in such systems has been physically, analytically, and experimentally investigated. This study analytically investigates the physical mechanisms of surge onset in turbo heat pumps. From an existing nonlinear turbo heat pump surge model, the turbo heat pump is viewed as a mass-spring-damper system with two inertias, two dampers, and four springs which is then further simplified to a single degree-of-freedom system. Surge onset occurs when the system damping becomes zero and depends not only the compressor but also on the ducts, heat exchangers, and expansion valve. Alternatively, a new stability model has been developed by applying a linearized small perturbation method to the nonlinear turbo heat pump surge model. When the new linear stability model is applied to a conventional open loop compression system (e.g., a turbocharger), predictions identical to those of Greitzer's model are obtained. In addition, surge onset has been experimentally measured in two turbo heat pumps. A comparison of the predictions and measurements shows that the mass-spring-damper model and the linearized stability model can accurately predict the turbo heat pump surge onset and the mass-spring-damper model can explain the turbo heat pump surge onset mechanisms and parametric trends in turbo heat pumps.

Experimental investigation on a capillary tube based transcritical CO 2 heat pump system

2017 ◽  
Vol 112 ◽  
pp. 184-189 ◽  
Author(s):  
Yulong Song ◽  
Jing Wang ◽  
Feng Cao ◽  
Pengcheng Shu ◽  
Xiaolin Wang
Keyword(s):  
Experimental Investigation ◽  
Heat Pump ◽  
Capillary Tube ◽  
Pump System ◽  
Heat Pump System

OS4-07 Study of the CO2-Heat Pump System Using the Capillary Tube : Part 2 Evaluation of Actual Operation Test

2005 ◽  
Vol 2005.10 (0) ◽  
pp. 175-176
Author(s):  
Keisuke TAKAYAMA ◽  
Kazuki HARAGUCHI ◽  
Yoshiharu AMANO ◽  
Takumi HASHIZUME ◽  
Michio SASAKI
Keyword(s):  
Heat Pump ◽  
Capillary Tube ◽  
Pump System ◽  
Heat Pump System ◽  
Operation Test ◽  
Actual Operation

ANALYTICAL STUDY ON THE HEATING PERFORMANCE OF A MULTI-TYPE HEAT PUMP SYSTEM WITH n-INDOOR UNITS

2011 ◽  
Vol 19 (01) ◽  
pp. 25-36 ◽  
Author(s):  
JONG WON CHOI ◽  
IL HWAN LEE ◽  
MIN SOO KIM
Keyword(s):  
Heat Pump ◽  
Heat Exchangers ◽  
Lumped Parameter Model ◽  
Distributed Model ◽  
Experimental Conditions ◽  
Pump System ◽  
Heat Pump System ◽  
Heating Performance ◽  
Lumped Parameter ◽  
Expansion Valve

This paper presents the steady-state heating performance of a multi-type heat pump system. The compressor and expansion valves are described by a lumped parameter model for its rapid and prompt response to the disturbances compared to those of the heat exchangers. Fully distributed model (or spatially dependent model) is used for the evaporator and condenser since the lumped method does not guarantee enough accuracy in estimating the performance of heat exchangers with phase change. Most researches on the numerical simulation in heat pump system focuses on the precise modeling for the steady or transient states while few researches on the simulations consider the relationships among several indoor units, expansion valve openings and compressor speed in multi-type heat pump system. In this study, the heating performance of a multi-type heat pump system using R410A with three indoor units is simulated for the investigation of system characteristics and the simulation results are verified for several experimental conditions. Finally, the simulation technique is extended to the system with n-indoor units.

Modeling of Surge Characteristics in Turbo Heat Pumps

2010 ◽  
Author(s):  
Hye Rim Kim ◽  
Seung Jin Song
Keyword(s):  
Gas Turbine ◽  
Heat Pump ◽  
Heat Pumps ◽  
Ideal Gas ◽  
Working Fluid ◽  
Pump System ◽  
Turbine Engine ◽  
Heat Pump System ◽  
Expansion Valve ◽  
Two Phases

This paper presents a new analytical model of surge dynamics in turbo heat pumps. Turbo heat pumps use refrigerants as the working fluid and consist of a centrifugal compressor, condenser, expansion valve, and evaporator. Compared to a gas turbine engine, the turbo heat pump system introduces additional complexities. First, the turbo heat pump forms a closed-loop system. Second, the system has two plenums — condenser and evaporator — which are coupled to each other. Third, the heat pump runs on a refrigeration cycle with two phases — vapor and liquid. Fourth, heat transfer effects of evaporation and condensation have to be considered. Fifth, unlike air, a refrigerant has strong real gas effects and thus cannot be modeled as an ideal gas. The new model addresses such additional complexities on the basis of the first principles of conservation of mass, momentum, and energy. When applied to a gas turbine system, the new model’s predictions become identical to those from the Greitzer’s model. Furthermore, comparison with the available experimental data shows that the model can also accurately predict surge behavior in actual turbo heat pumps. Finally, the effects of Greitzer’s B parameter and the ratio of evaporator and condenser volume have been examined. Parameter B influences both surge shape and frequency. Finally, surge frequency is extremely sensitive to the ratio of the two plenum volumes.

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