scholarly journals Analysis and Comparison of Some Low-Temperature Heat Sources for Heat Pumps

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1853 ◽  
Author(s):  
Pavel Neuberger ◽  
Radomír Adamovský
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Ambient Air ◽  
Heat Transfer Fluid ◽  
Heat Sources ◽  
Ground Heat Exchangers ◽  
Temperature Heat

The efficiency of a heat pump energy system is significantly influenced by its low-temperature heat source. This paper presents the results of operational monitoring, analysis and comparison of heat transfer fluid temperatures, outputs and extracted energies at the most widely used low temperature heat sources within 218 days of a heating period. The monitoring involved horizontal ground heat exchangers (HGHEs) of linear and Slinky type, vertical ground heat exchangers (VGHEs) with single and double U-tube exchanger as well as the ambient air. The results of the verification indicated that it was not possible to specify clearly the most advantageous low-temperature heat source that meets the requirements of the efficiency of the heat pump operation. The highest average heat transfer fluid temperatures were achieved at linear HGHE (8.13 ± 4.50 °C) and double U-tube VGHE (8.13 ± 3.12 °C). The highest average specific heat output 59.97 ± 41.80 W/m2 and specific energy extracted from the ground mass 2723.40 ± 1785.58 kJ/m2·day were recorded at single U-tube VGHE. The lowest thermal resistance value of 0.07 K·m2/W, specifying the efficiency of the heat transfer process between the ground mass and the heat transfer fluid, was monitored at linear HGHE. The use of ambient air as a low-temperature heat pump source was considered to be the least advantageous in terms of its temperature parameters.

Determination of Heat Transfer Characteristics of Solar Thermal Collectors as Heat Source for a Residential Heat Pump

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Maarten G. Sourbron ◽  
Nesrin Ozalp
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
Solar Collector ◽  
Heat Transfer Characteristics ◽  
Pump System ◽  
Heat Pump System ◽  
Temperature Heat

With reducing energy demand and required installed mechanical system power of modern residences, alternate heat pump system configurations with a possible increased economic viability emerge. Against this background, this paper presents a numerically examined energy feasibility study of a solar driven heat pump system for a low energy residence in a moderate climate, where a covered flat plate solar collector served as the sole low temperature heat source. A parametric study on the ambient-to-solarfluid heat transfer coefficient was conducted to determine the required solar collector heat transfer characteristics in this system setup. Moreover, solar collector area and storage tank volume were varied to investigate their impact on the system performance. A new performance indicator “availability” was defined to assess the contribution of the solar collector as low temperature energy source of the heat pump. Results showed that the use of a solar collector as low temperature heat source was feasible if its heat transfer rate (UA-value) was 200 W/K or higher. Achieving this value with a realistic solar collector area (A-value) required an increase of the overall ambient-to-solarfluid heat transfer coefficient (U-value) with a factor 6–8 compared to the base case with heat exchange between covered solar collector and ambient.

Determination of Heat Transfer Characteristics of Solar Thermal Collectors as Heat Source for a Residential Heat Pump

2015 ◽  
Author(s):  
Maarten G. Sourbron ◽  
Nesrin Ozalp
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Low Temperature ◽  
Heat Source ◽  
Transfer Coefficient ◽  
Heat Pump ◽  
Solar Collector ◽  
Solar Thermal ◽  
Heat Transfer Characteristics ◽  
Temperature Heat

One of the best ways of making efficient use of energy in residential units is to use heat pump. Heat pump performance can be further enhanced by integrating a solar thermal unit to provide hot water and subsidize space heating. This paper presents numerically examined energy feasibility study of a solar driven heat pump system for a low energy residence, where a flat plate solar collector served as the sole low temperature heat source. A parametric study on the ambient-to-solar fluid heat transfer coefficient has been conducted to determine the required solar collector heat transfer characteristics in this system. Solar collector area and storage tank volume were varied to investigate their impact on the system performance. A new performance indicator availability was defined to assess the contribution of the solar collector as low temperature energy source of the heat pump. Results showed that the use of a solar collector as low temperature heat source was feasible if its heat transfer rate (UA-value) was 200 W/K or higher. Achievement of this value with a realistic solar collector area (A-value) required an increase of the overall ambient-to-solar fluid heat transfer coefficient (U-value) with a factor of 6 to 8 compared to the base case with only natural convection heat exchange between solar collector cover and ambient.

Application Study of Newly Developed Turbo Heat Pump for 130 Degrees Celsius Water for an Industrial Process

2011 ◽  
Author(s):  
Shuichi Umezawa ◽  
Haruo Amari ◽  
Hiroyuki Shimada ◽  
Takashi Matsuhisa ◽  
Ryo Fukushima ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
High Efficiency ◽  
Industrial Process ◽  
Application Study ◽  
Hot Air ◽  
Heat Demand ◽  
Temperature Heat

This paper reports application study of newly developed turbo heat pump for 130 degrees Celsius (°C) water for an industrial process in an actual factory. The heat pump is characterized by high efficiency and large heat output, by using a state-of-the-art turbo compressor. The heat pump requires a low temperature heat source in order to achieve high efficiency. The heat demand is for several drying furnaces in the factory, which requires producing hot air of 120 °C. The heat exchanger was designed to produce the hot air. Experiments were conducted to confirm the performance of the heat exchanger under a reduced size of the heat exchanger. Low temperature heat sources are from both exhaust gas of the drying furnaces and that of an annealing furnace. The heat exchangers were also designed to recover heat of the exhaust gas from the two types of furnace. A thermal storage tank was prepared for the low temperature heat source, and for adjusting the time difference between the heat demand and the low temperature heat source. The size of the tank was determined by considering the schedule of furnaces operations. As a result of the present study, it was confirmed that the heat pump was able to satisfy the present heat demand while retaining high efficiency. Primary energy consumption and CO2 emission of the heat pump were calculated on the basis of the present results in order to compare them with those of the boilers.

scholarly journals Ground-Coupled Natural Circulating Devices (Thermosiphons): A Review of Modeling, Experimental and Development Studies

Inventions ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 14
Author(s):  
Messaoud Badache ◽  
Zine Aidoun ◽  
Parham Eslami-Nejad ◽  
Daniela Blessent
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Low Temperatures ◽  
Experimental Studies ◽  
Heat Transfer Fluid ◽  
Fluid Circulation ◽  
Ground Heat Exchangers ◽  
Additional Equipment ◽  
Different Types ◽  
Overall Efficiency

Compared to conventional ground heat exchangers that require a separate pump or othermechanical devices to circulate the heat transfer fluid, ground coupled thermosiphons or naturallycirculating ground heat exchangers do not require additional equipment for fluid circulation in theloop. This might lead to a better overall efficiency and much simpler operation. This paper providesa review of the current published literature on the different types of existing ground coupledthermosiphons for use in applications requiring moderate and low temperatures. Effort has beenfocused on their classification according to type, configurations, major designs, and chronologicalyear of apparition. Important technological findings and characteristics are provided in summarytables. Advances are identified in terms of the latest device developments and innovative conceptsof thermosiphon technology used for the heat transfer to and from the soil. Applications arepresented in a novel, well-defined classification in which major ground coupled thermosiphonapplications are categorized in terms of medium and low temperature technologies. Finally,performance evaluation is meticulously discussed in terms of modeling, simulations, parametric,and experimental studies.

Thermodynamic peculiarities of alpha-type Stirling engines for low-temperature difference power generation: Optimisation of operating parameters and heat exchangers using a third-order model

2013 ◽  
Vol 228 (11) ◽  
pp. 1936-1947 ◽  
Author(s):  
Benedikt Hoegel ◽  
Dirk Pons ◽  
Michael Gschwendtner ◽  
Alan Tucker ◽  
Mathieu Sellier
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Operating Parameters ◽  
Heat Sources ◽  
Third Order ◽  
Concentrated Solar Energy ◽  
Stirling Engines ◽  
Temperature Heat

Low-temperature heat sources such as waste heat and geothermal energy in the range from 100 ℃ to 200 ℃ are widely available and their potential is largely untapped. Stirling engines are one possibility to convert this heat to a usable power output. Much work has been done to optimise Stirling engines for high-temperature heat sources such as external combustion or concentrated solar energy but only little is known about suitable engine layouts at lower temperature differences. With the reduced temperature difference, changes become necessary not only in the heat exchangers and the regenerator but also in the operating parameters such as frequency and phase angle. This paper shows results obtained from a third-order simulation model that help to identify beneficial parameter combinations, and explains the differences of low and high-temperature engines.

A New Combined Power and Cooling Cycle for Low Temperature Heat Sources

2003 ◽  
Author(s):  
D. Y. Goswami ◽  
Gunnar Tamm ◽  
Sanjay Vijayaraghavan
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Waste Heat ◽  
Experimental System ◽  
Operating Conditions ◽  
Working Fluid ◽  
Second Law ◽  
Heat Sources ◽  
Vapor Generation ◽  
Temperature Heat

A new thermodynamic cycle has been developed for the simultaneous production of power and cooling from low temperature heat sources. The proposed cycle combines the Rankine and absorption refrigeration cycles, providing power and cooling in desired ratios to best suit the application. A binary mixture of ammonia and water is used as the working fluid, providing a good thermal match with the sensible heat source over a range of boiling temperatures. Due to its low boiling point, the ammonia-rich vapor expands to refrigeration temperatures while work is extracted through the turbine. Absorption condensation of the vapor back into the bulk solution occurs near ambient temperatures. The proposed cycle is suitable as a bottoming cycle using waste heat from conventional power generation systems, or can utilize low temperature solar or geothermal renewable resources. The cycle can be scaled to residential, commercial or industrial uses, providing power as the primary goal while satisfying some of the cooling requirements of the application. The cycle is under both theoretical and experimental investigations. Initial parametric studies of how the cycle performs at various operating conditions showed the potential for the cycle to be optimized. Optimization studies performed over a range of heat source and heat sink temperatures showed that the cycle could be optimized for maximum work or cooling output, or for first or second law efficiencies. Depending on the heat source temperatures, as much as half of the output may be obtained as refrigeration under optimized conditions, with refrigeration temperatures as low as 205 K being achievable. Maximum second law efficiencies over 60% have been found with the heat source between 350 and 450 K. An experimental system was constructed to verify the theoretical results and to demonstrate the feasibility of the cycle. The investigation focused on the vapor generation and absorption processes, setting up for the power and refrigeration studies to come later. The turbine was simulated with an equivalent expansion process in this initial phase of testing. Results showed that the vapor generation and absorption processes work experimentally, over a range of operating conditions and in simulating the sources and sinks of interest. The potential for combined work and cooling output was evidenced in operating the system. Comparison to ideally simulated results verified that there are thermal and flow losses present, which were assessed to make both improvements in the experimental system and modifications in the simulations to include realistic losses.

Experimental Results of an Ammonia-Water Mixture Turbine System: Effectiveness With a Low Temperature Heat Source

2004 ◽  
Author(s):  
Keisuke Takeshita ◽  
Kouji Morimoto ◽  
Yoshiharu Amano ◽  
Takumi Hashizume
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Steam Turbine ◽  
Back Pressure ◽  
Experimental Results ◽  
Water Mixture ◽  
Heat Sources ◽  
Sensible Heat ◽  
Ammonia Water ◽  
Temperature Heat

This paper presents an experimental investigation of the effectiveness of an AWM (Ammonia-Water Mixture) turbine system with low temperature heat sources. The AWM turbine system (AWMTS) features Kalina cycle technology, namely, it employs an ammonia-water mixture as the working fluid and includes a separation / absorption process of NH3-H2O. Since AWM is a non-azeotropic mixture, its temperature changes during evaporation and condensation. This behavior gives AWMTS the advantage of heat recovery from a sensible heat source such as exhaust gas. It is known that an AWMTS can generate more power than a Rankine cycle system from 250–650°C sensible heat sources. The authors constructed a 70 KW-experimental facility and investigated the practical applications of AWMTS. It is located at the bottoming stage below a conventional combined cycle composed of a gas turbine and a steam turbine. Its heat source is the exhaust steam from a back pressure steam turbine at the middle stage of the system. The experiment was carried out with changing the back pressure of the steam turbine. The experimental results show that power generation is possible from 138 to 162 °C heat source steam.

scholarly journals Thermodynamic analysis of the heat pump steam system with medium-low temperature heat source

2021 ◽  
Vol 7 ◽  
pp. 266-278
Author(s):  
Shuaiqi Li ◽  
Shihui He ◽  
Wenji Song ◽  
Zipping Feng
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
Thermodynamic Analysis ◽  
Temperature Heat ◽  
Steam System

scholarly journals Simulation Analysis on the Heat Performance of Deep Borehole Heat Exchangers in Medium-Depth Geothermal Heat Pump Systems

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 754 ◽  
Author(s):  
Jiewen Deng ◽  
Qingpeng Wei ◽  
Shi He ◽  
Mei Liang ◽  
Hui Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Geothermal Energy ◽  
Heat Transfer Performance ◽  
Deep Borehole ◽  
Geothermal Heat ◽  
Temperature Heat ◽  
Geothermal Heat Pump ◽  
Borehole Heat Exchangers

Deep borehole heat exchangers (DBHEs) extract heat from the medium-depth geothermal energy with the depth of 2–3 km and provide high-temperature heat source for the medium-depth geothermal heat pump systems (MD-GHPs). This paper focuses on the heat transfer performance of DBHEs, where field tests and simulation are conducted to analyze the heat transfer process and the influence factors. Results identify that the heat transfer performance is greatly influenced by geothermal properties of the ground, thermal properties and depth of DBHEs and operation parameters, which could be classified into external factors, internal factors and synergic adjustment. In addition, the long-term operation effects are analyzed with the simulation, results show that with inlet water temperature setting at 20 °C and flow rate setting at 6.0 kg/s, the average outlet water temperature only drops 0.99 °C and the average heat extraction drops 9.5% after 20-years operation. Therefore, it demonstrates that the medium-depth geothermal energy can serve as the high-temperature heat source for heat pump systems stably and reliably. The results from this study can be potentially used to guide the system design and optimization of DBHEs.

THE ANALYSIS OF EXERGY EFFICIENCY IN THE LOW TEMPERATURE HEAT EXCHANGER

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3497-3499 ◽  
Author(s):  
LAN PENG ◽  
YOU-RONG LI ◽  
SHUANG-YING WU ◽  
BO LAN
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Exchanger ◽  
Low Temperature ◽  
Transfer Process ◽  
Heat Exchangers ◽  
Heat Transfer Process ◽  
Exergy Efficiency ◽  
Capacity Ratio ◽  
Temperature Heat

Based on the analyzing of the thermodynamic performance of the heat transfer process in the low temperature heat exchangers, the exergy efficiency of the heat transfer process is defined and a general expression for the exergy efficiency is derived, which can be used to discuss the effect of heat transfer units number and heat capacity ratio of fluids on the exergy efficiency of the low temperature heat exchanger. The variation of the exergy efficiency for several kinds of flow patterns in the low heat exchangers is compared and the calculating method of the optimal values of heat capacity ratio for the maximum exergy efficiency is given.

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