Journal of Drainage and Irrigation Machinery Engineering
Doi: 10.3969/j. issn.1674－8530.paper number
Title in English
Author A1,2,Author B2, Author C3, Author D3
(1. Affiliation 1, City 1 Post Code 1, nation 1; 2. Affiliation 2, City 2 Post Code 2, nation 2; 3. Affiliation 3, City 3 Post Code 3, nation 3)
Abstract: The scope of this work is to investigate the performance of the multi-type heat pump system. Numerical methods are provided to analyze dynamic characteristics as well as steady-state performance of a multi-type heat pump system. Lumped parameter method was applied to simulate the compressor and expansion device. Additionally, fully distributed method was used for analyzing the condenser and evaporators. The transient terms in the governing equations for heat exchangers were solved adopting the wave equation solutions. The simulation results predict the steady-state performance of a heat pump system with the deviation of ±10%. The transient simulation showed satisfactory responses of temperatures and pressures for various compressor speeds or expansion valve openings. From the results, it was shown that the operating conditions of secondary fluid of one indoor unit had minor influence on the performance of the other unit, while opening of expansion valve affected the transient responses of both evaporators significantly.
Key words: word1;word2;word3;word4;word5
CLC Number: S277 Document Code: A Article No: 1674－8530(publishing year)××－××××－××
Citation: Author A, Author B, Author C, et al. Title in English[J]. Journal of Drainage and Irrigation Machinery Engineering, year, volume(issue): page-page.
论文模版
1 Introduction
As higher standard of living is pursued, there is a tendency that multi-type heat pump is installed in a house, which can satisfy the needs for the installation of several individual indoor units while it has only one outdoor unit. With respect to cost and space, multi-type heat pump system has much more merits than conventional HVAC system. However, the system’s complexity and lack of control strategy on a multi-typeheat pump system hinder its appearance as a major air conditioning system in the market. Many researchers investigated the refrigeration system through experimental methods to analyze the performance because it is difficult to simulate the refrigeration system due to its complexity in thermodynamic processes such as phase change which occurs almost everywhere in the refrigeration system. Early works on the numerical simulation of the transient performance was used as a basic criterion to construct a new system or modify existing system[1-2].
In this study, the numerical simulations for a multi-typeheat pump are presented. When we control the capacity of thesystem, the system stays in the transient state for the mostpart of its operation. It takes considerable time for the systemto reach another steady-state, and the system may reachunwanted operation state where the system gives out poorperformance. Therefore, we have to analyze the transientcharacteristics as well as the steady-state performance.
2 Simulation procedures
The compressor in this study was regarded as a scroll type compressor. When the compressor is simulated numerically,two important concepts should be considered. One is the mechanical inertia that is affected by the mechanical driving part and the other is the thermal inertia influenced by the variations of external heat transfer situation. The simple compressor model based on the volumetric efficiency is chosen.
2.1 Compressor modeling methods
2.1.1 Heat transfer coefficients and void fraction models
The procedures of discretization and the final forms of governing equations are decided by following steps. In a steady-state simulation, the discretization equations derived from the continuity equation and the energy equation for
refrigerant are expressed as following equation:
, (1)
The secondary fluid was regarded as water and the inlet temperature was maintained at fixedvalue. The evaluation cases are listed in Tab.1.
Tab.1 Table title in English (be placed at the center)
Compressor / LEV opening / /(g·s-1) / /
(g·s-1) / /
℃
40 / 340 / 84.85 / 82.11 / 26.81
40 / 360 / 84.87 / 81.94 / 26.72
40 / 350 / 85.03 / 82.27 / 26.67
40 / 330 / 84.99 / 82.34 / 29.66
40 / 360 / 84.80 / 81.90 / 26.71
40 / 350 / 85.01 / 82.21 / 26.61
40 / 330 / 84.92 / 82.31 / 29.62
In order to well represent the flow field, streamline distribution in impelleris shown in Fig.1.
Fig.1 Figure title in English (be placed at the center)
3 Conclusions
In this study, the steady-state evaluation and the dynamic simulation are performed for a single type and a multi-type heat pump system. By comparing the numerical results with experiment data, the numerical simulation of this study shows a good agreement.
The interrelationships between indoor units were investigated in the multi-type heat pump. From the steady-state evaluation, it was shown that the inlet states of the secondary fluid gave trivial effect on the other indoor unit, however, the change in the opening of LEV made changes in the system significantly. Similar trends to the steady simulation were found in the transient simulation.
The simulation methods of this study can be applied to construct a new system, evaluate an existing system or design a controller for the refrigeration system.
Acknowledgements
The authors wish to thank Region Nord-Pas de Calais and CNRS for their financial support in the frame of the CISIT program and Mrs Giovanni Cavazzini (University of
Padova) for extended data reduction results.
Nomenclature
density(m)
A area(m2)
t time(s)
mass flow rate(g·s-1)
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