403 Analysis of Temperature Distribution in a Storage Tank of a CO_2 Heat Pump Water Heating System : Analysis of Extraction of Medium Temperature Water

2007 ◽  
Vol 2007.17 (0) ◽  
pp. 261-264
Author(s):  
Tetsuya WAKUI ◽  
Ryohei YOKOYAMA ◽  
Junya KAMAKARI
Keyword(s):  
Temperature Distribution ◽  
Heat Pump ◽  
Storage Tank ◽  
System Analysis ◽  
Heating System ◽  
Water Heating ◽  
Medium Temperature ◽  
Temperature Water

scholarly journals Numerical Analysis for Performance Evaluation of a Multi-Functional CO2 Heat Pump Water Heating System

2018 ◽  
Vol 8 (10) ◽  
pp. 1829 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Masashi Ohkura ◽  
Takuya Nakamata ◽  
Tetsuya Wakui
Keyword(s):  
Heat Pump ◽  
System Performance ◽  
Storage Tank ◽  
Heating System ◽  
Functional System ◽  
Hot Water ◽  
System Efficiency ◽  
Water Heating ◽  
Perfect Mixing ◽  
Component Models

In recent years, CO2 heat pump water heating systems have been developed, and their performances have been enhanced while their functions have been expanded. In a multi-functional system, used for both hot water supply and bath heating, hot water retrieved from the top of a storage tank is returned to its bottom or side after heat exchange for bath heating, which destroys the stratified temperature distribution in the storage tank and degrades the system performance. In this paper, the performance of a multi-functional CO2 heat pump water heating system has been evaluated by numerical simulation. A system model was created by combining component models for a CO2 heat pump, mixing valves, a storage tank, a heat exchanger, and a bathtub. Partly, perfect mixing by hot water return was assumed in the component model for the storage tank, and its validity was verified through experiments. A performance analysis has been conducted under daily repeated hot water and bath heating demands, and the system performance was evaluated at a periodically steady state. As a result, the system efficiency and the volume of unused hot water in the multi-functional system decreased by 4.9% and 16.3%, respectively, as compared to those in the uni-functional system, when hot water returned to the bottom of the storage tank. When the position for hot water return is heightened, the system efficiency becomes higher than that in the uni-functional system, while the volume of unused hot water decreases furthermore.

Influence of ambient temperatures on performance of a CO2 heat pump water heating system

Energy ◽  
2007 ◽  
Vol 32 (4) ◽  
pp. 388-398 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Takeshi Shimizu ◽  
Koichi Ito ◽  
Kazuhisa Takemura
Keyword(s):  
Heat Pump ◽  
Heating System ◽  
Water Heating ◽  
Ambient Temperatures

A TRNSYS/GROCS Simulation of the TECH House I Ground-Coupled Series Solar-Assisted Heat Pump System

1983 ◽  
Vol 105 (4) ◽  
pp. 446-453 ◽  
Author(s):  
D. J. Roeder ◽  
R. L. Reid
Keyword(s):  
Heat Pump ◽  
Storage Tank ◽  
Heating System ◽  
Electric Resistance ◽  
Heating Season ◽  
Pump System ◽  
Heat Pump System ◽  
Seasonal Performance ◽  
The University ◽  
Better Than

The series solar-assisted heat pump heating system with ground-coupled storage in The University of Tennessee’s TECH House I in Knoxville, Tennessee, has been modeled using TRNSYS/GROCS and was compared to the experimental performance for the 1980–81 heating season. The simulation results were within 8 percent of the experimental measurements. Both simulation and experimental results showed that ground coupling of thermal storage led to the elimination of electric resistance backup heat and a large reduction in the peak heating demand of the house. Results of a parametric study showed that, in general, a ground-coupled storage tank performs better than a storage tank placed outdoors in the Knoxville area. Application of a next generation heat pump resulted in the most significant impact on the seasonal performance factor. As expected, higher performance collectors and larger collector areas led to higher system seasonal performance. An economic analysis showed that the series solar heat pump system cannot economically compete with the stand-alone heat pump system in the Knoxville area.

A Second Law Approach to Characterising Thermally Stratified Hot Water Storage With Application to Solar Water Heaters

1999 ◽  
Vol 121 (4) ◽  
pp. 194-200 ◽  
Author(s):  
G. Rosengarten ◽  
G. Morrison ◽  
M. Behnia
Keyword(s):  
Temperature Distribution ◽  
Heat Exchangers ◽  
Water Storage ◽  
Heating System ◽  
Hot Water ◽  
Effect Of Temperature ◽  
Storage Efficiency ◽  
Water Heating ◽  
Solar Water Heating ◽  
Solar Water

This paper presents a method of characterising and evaluating the performance of hot water storage systems in terms of their temperature distribution. The change in exergy from the stratified state to the delivery state depends on the stored energy and the stratification. It can thus he used to define the storage efficiency for sensible heat storage devices. A new parameter that isolates the stratification component of the exergy is defined and called the stratification efficiency. The effect of temperature distribution, delivery temperature and tank cross-section on exergy and stratification efficiency is investigated. The advantage that stratification offers over a mixed tank is examined in terms of the storage efficiency and overall solar water heating system performance. Exergy is used to assess the operation of mantle heat exchangers in solar water heating systems and it is shown that exergy and stratification efficiency, as well as energy, should be used to ascertain the performance of such heat exchangers.

Performance analysis of a CO2 heat pump water heating system under a daily change in a standardized demand

Energy ◽  
2010 ◽  
Vol 35 (2) ◽  
pp. 718-728 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Tetsuya Wakui ◽  
Junya Kamakari ◽  
Kazuhisa Takemura
Keyword(s):  
Performance Analysis ◽  
Heat Pump ◽  
Heating System ◽  
Water Heating ◽  
Daily Change
Sign in / Sign up

Export Citation Format

Share Document