Linear Stability Analysis of Turbo Heat Pumps

2012 ◽  
Author(s):  
Jung Chan Park ◽  
Kil Young Kim ◽  
Jinhee Jeong ◽  
Seung Jin Song
Keyword(s):  
Heat Exchange ◽  
Linear Stability ◽  
Heat Pump ◽  
Closed Loop ◽  
Loop System ◽  
Working Fluid ◽  
Two Phase ◽  
Pump System ◽  
Heat Pump System ◽  
New Model

A typical turbo heat pump system consists of a centrifugal compressor, expansion valve, and two heat exchangers or plenums — 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 working fluid. For such systems, a new linear stability model has been developed by applying a linearized small perturbation method to the nonlinear turbo heat pump surge model. When the new linear model is applied to a compressor in an open loop system (e.g. turbocharger), results identical to those of Greitzer’s model are obtained. When applied to an operating turbo heat pump, the new model accurately predicts the surge onset point. Finally, results from a parametric study on the influence of the B parameter on surge onset are presented. Thus, the new model can be applied to predict stability of various compression systems — either open or closed-loop systems running single or two-phase working fluids with or without heat exchange.

scholarly journals Evaluation of Suitable Areas to Introduce a Closed-Loop Ground Source Heat Pump System in the Case of a Standard Japanese Detached Residence

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4294
Author(s):  
Gaurav Shrestha ◽  
Mayumi Yoshioka ◽  
Hikari Fujii ◽  
Youhei Uchida
Keyword(s):  
Heat Exchange ◽  
Heat Pump ◽  
Closed Loop ◽  
Ground Source Heat Pump ◽  
Standard Size ◽  
Pump System ◽  
Heat Pump System ◽  
The North ◽  
Ground Source ◽  
Suitability Map

Evaluation of appropriate areas to introduce a closed-loop ground-source heat pump (GSHP) system in the case of a standard detached residence was conducted in Akita Plain, Japan. Depth of borehole heat exchanger (BHE) required to use a GSHP system was taken as the suitability index, which is simpler for the general public to understand and to promote the system. Heating and cooling loads of the standard size detached residence were calculated based on the 2013 Energy Conservation Standard. To estimate BHE depths and estimate a suitable area, identical 3D BHE models were constructed at 30 points in the plain. Required BHE depths were determined by performing heat exchange simulations at each location using the calculated loads and heat exchange rates. A suitability map showing distribution of the required BHE depths was prepared. BHE depths were shorter in the north-western area compared to the other parts, implying that the coastal lowlands in this area are more suitable for closed-loop system in the standard detached residences in terms of heat exchange performance as well as the cost reduction. Thickly distributed Quaternary System with higher thermal conductivity is contributing to shorter BHE depths. The suitability map is effective to adopt potential areas for the system installation in the standard detached Japanese residences.

Optimization of Working Ground Heat Storage With Seasonal Regeneration

2006 ◽  
Author(s):  
Pawel Olszewski
Keyword(s):  
Energy Storage ◽  
Heat Exchange ◽  
Heat Pump ◽  
Input Data ◽  
Heat Storage ◽  
Target Function ◽  
Working Fluid ◽  
Solar Collectors ◽  
Pump System ◽  
Heat Pump System

The aim of the research was an optimization of long-term heat storage with seasonal regeneration. Energy consumption for central heating during wintertime, transfererred from ground energy storage using a heat exchange device, is the operating principle of such systems. Warmed working fluid is then used in a heat pump system. However, more accurate calculations showed that over time of usage, there is a trend toward cooling at deeper round layers. Such a situation leads to a lowering of ground potential when using heat pump systems. A possible solution to this problem is the application of summer regeneration: during summer months, the working fluid is firstly warmed in solar collectors, and then forced into the same boreholes. The numerical model of a vertical, ground heat exchange device (configured as a "pipe in pipe", known as a Fields' pipe) was specially developed. Temperature distribution of the working fluid along the pipe was one of the boundary conditions, for the co-axial, time-variable, heat conduction task, which described the heat flow in energy storage. The numerical simulation of solar collectors work was based on the Hottel - Whillier - Bliss equation, in which energy flow from the solar collector is calculated, dependant on external parameters such as: insulation or ambience temperature. The combination of three computational parts- the ground heat exchange device, energy storage area and solar collectors battery- allows the target function to be defined for task optimization. The subject of optimization was an energy quantity, which can be taken from energy underground storage, and then utilized by the heat pump system. In the summarized paper, a combination of the input data, which influenced the efficiency of energy storage, was chosen. Hypothetical data were: outside diameter and length of heat exchange device, distance between pipes, fluid flow through the pipe during charge and discharge processes or temperature of inlet working fluid. The influence of individual parameters on the target function, holding all input data constant, was analyzed. A developed evolutionary numerical code known as GENOCOP I (GEnetic algorithm for Numerical Optimization for COnstrained Problems) [3] was used for optimization. After preliminary correction of boundary values of the input data, nine attempts of optimization were taken up. The research results identified optimal values of input parameters for which maximum energy could be taken from ground storage.

scholarly journals Analysis of Heat Exchange Rate for Low-Depth Modular Ground Heat Exchanger through Real-Scale Experiment

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1893
Author(s):  
Kwonye Kim ◽  
Jaemin Kim ◽  
Yujin Nam ◽  
Euyjoon Lee ◽  
Eunchul Kang ◽  
...  
Keyword(s):  
Exchange Rate ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Pump ◽  
Heat Extraction ◽  
Ground Heat Exchanger ◽  
Pump System ◽  
Heat Pump System ◽  
Scale Experiment ◽  
Real Scale

A ground source heat pump system is a high-performance technology used for maintaining a stable underground temperature all year-round. However, the high costs for installation, such as for boring and drilling, is a drawback that prevents the system to be rapidly introduced into the market. This study proposes a modular ground heat exchanger (GHX) that can compensate for the disadvantages (such as high-boring/drilling costs) of the conventional vertical GHX. Through a real-scale experiment, a modular GHX was manufactured and buried at a depth of 4 m below ground level; the heat exchange rate and the change in underground temperatures during the GHX operation were tracked and calculated. The average heat exchanges rate was 78.98 W/m and 88.83 W/m during heating and cooling periods, respectively; the underground temperature decreased by 1.2 °C during heat extraction and increased by 4.4 °C during heat emission, with the heat pump (HP) working. The study showed that the modular GHX is a cost-effective alternative to the vertical GHX; further research is needed for application to actual small buildings.

Experimental Study of Heating-Cooling Combined Ground Source Heat Pump System with Horizontal Ground Heat Exchanger

2011 ◽  
Vol 374-377 ◽  
pp. 398-404 ◽  
Author(s):  
Ying Ning Hu ◽  
Ban Jun Peng ◽  
Shan Shan Hu ◽  
Jun Lin
Keyword(s):  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Pump ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Ground Heat Exchanger ◽  
Pipe Length ◽  
Pump System ◽  
Heat Pump System ◽  
Heating And Cooling

A hot-water and air-conditioning (HWAC) combined ground sourse heat pump(GSHP) system with horizontal ground heat exchanger self-designed and actualized was presented in this paper. The heat transfer performance for the heat exchanger of two different pipe arrangements, three layers and four layers, respectively, was compared. It showed that the heat exchange quantity per pipe length for the pipe arrangement of three layers and four layers are 18.0 W/m and 15.0 W/m. The coefficient of performance (COP) of unit and system could remain 4.8 and 4.2 as GSHP system for heating water, and the COP of heating and cooling combination are up to 8.5 and 7.5, respectively. The power consumption of hot-water in a whole year is 9.0 kwh/t. The economy and feasibility analysis on vertical and horizontal ground heat exchanger were made, which showed that the investment cost per heat exchange quantity of horizontal ground heat exchanger is 51.4% lower than that of the vertical ground heat exchanger, but the occupied area of the former is 7 times larger than the latter's.

Water Heating and Dehumidification With Heat Pump Utilizing Solar, Ambient and Waste Heat

2009 ◽  
Author(s):  
M. N. A. Hawlader ◽  
Zakaria Mohd. Amin ◽  
Shaochun Ye ◽  
Kyaw Thura Win
Keyword(s):  
Heat Pump ◽  
Waste Heat ◽  
Solar Irradiation ◽  
Water Heating ◽  
Two Phase ◽  
Pump System ◽  
Heat Pump System ◽  
A Value ◽  
National University ◽  
Collector Efficiency

The low temperature operation of a heat pump makes it an excellent match for the use of solar energy. At the National University of Singapore, a solar assisted heat pump system has been designed, fabricated and installed to provide water heating and drying. The system also utilizes the air con waste heat, which would normally be released to atmosphere adding to global warming. Experimental results show that the two-phase unglazed solar evaporator-collector, instead of losing energy to the ambient, gained a significant amount due to low operating temperature of the collector. As a result, the collector efficiency attains a value greater than 1, when conventional collector equations are used. With this evaporator-collector, the system can be operated even in the absence of solar irradiation. The waste heat was collected from an air-con system, which maintained a room at 20–22 °C. In the condenser side, water at 60 °C was produced at a rate of 3 liter/minute and the drying capacity was 2.2kg/hour. Maximum COP of the system was found to be about 5.5.

Modelling of an Indirect Solar-Assisted Heat Pump System for a High Performance Residential House

2013 ◽  
Author(s):  
Jenny Chu ◽  
Cynthia A. Cruickshank ◽  
Wilkie Choi ◽  
Stephen J. Harrison
Keyword(s):  
Heat Pump ◽  
High Performance ◽  
Simulation Software ◽  
Hot Water ◽  
Solar Thermal ◽  
Working Fluid ◽  
Space Heating ◽  
Pump System ◽  
Heat Pump System ◽  
Solar Thermal Collectors

Heat pumps are commonly used for residential space-heating and cooling. The combination of solar thermal and heat pump systems as a single solar-assisted heat pump (SAHP) system can significantly reduce residential energy consumption in Canada. As a part of Team Ontario’s efforts to develop a high performance house for the 2013 DOE Solar Decathlon Competition, an integrated mechanical system (IMS) consisting of a SAHP was investigated. The system is designed to provide domestic hot water, space-heating, space-cooling and dehumidification. The system included a cold and a hot thermal storage tank and a heat pump to move energy from the low temperature reservoir, to the hot. The solar thermal collectors supplies heat to the cold storage and operate at a higher efficiency due to the heat pump reducing the temperature of the collector working fluid. The combination of the heat pump and solar thermal collectors allows more heat to be harvested at a lower temperature, and then boosted to a suitable temperature for domestic use via the heat pump. The IMS and the building’s energy loads were modeled using the TRNSYS simulation software. A parametric study was conducted to optimize the control, sizing and configuration of the system. This paper provides an overview of the model and summarizes the results of the study. The simulation results suggested that the investigated system can achieve a free energy ratio of about 0.583 for a high performance house designed for the Ottawa climate.

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