Thermal Pump Research Articles

Efficient and sensitive detection of absorptive defects in fused silica optics based on laser thermal pumping combined with micro-interferometric imaging.

A novel, efficient, and sensitive method for detecting absorptive defects in fused silica optics, called laser thermal pumping combined with micro-interferometric imaging (LTP-MII), is proposed. First, the thermal deformation simulation of fused silica optics under a 355-nm LTP was calculated using a multiphysics field approach. Even with ppm-level absorption on the surface, a 600-W/mm2 LTP power density could induce a 2.1-nm deformation within the detection range of the MII. Subsequently, an LTP-MII system was constructed, comprising a 355-nm LTP spot with a 0.45-mm diameter and a white-light MII. Results from different fused silica samples showed that, at the same LTP power density of 19.5 W/mm2, the induced thermal deformation followed this order: 5% absorption thin film (75.3 nm) > a full brittle fracture pit defect (27.8 nm) > a scratch defect (5.2 nm). However, no thermal deformation was observed for the super-smooth polishing low-absorption substrate under these conditions, though it exhibited a deformation of 13.31 nm when the LTP power density reached 110.7 W/mm2. In addition, thermal deformation was positively correlated with the LTP power densities. These results demonstrate that LTP-MII is an efficient and sensitive method for reflecting the photo-thermal absorption characteristics of surface defects in fused silica optics.

Recent Research Progress in Microchannel Heat Sink Technology

As electronic devices continue to miniaturize and experience higher power densities, thermal management has become a critical factor limiting their performance and reliability. Microchannel heat sinks (MCHS) have emerged as a promising heat dissipation solution due to their excellent thermal performance and compact structure. Thermal resistance and pump power are two key performance indicators of MCHS. In recent years, significant efforts have been made to enhance the heat dissipation capacity of MCHS and reduce pump power, leading to numerous research achievements. This paper reviews the recent progress in microchannel heat sink research, including its working principles, design optimization, manufacturing processes, performance evaluation, and applications in various fields. Additionally, the challenges faced by MCHS and future development directions are discussed

Equivalent combined cycle modelling for three-heat-reservoir thermal Brownian heat pump with heat-transfer effect and its optimal performance

Equivalent combined cycle modelling for three-heat-reservoir thermal Brownian heat pump with heat-transfer effect and its optimal performance

Fewer temperature ties: scalable integration and broad selection of phase change materials for both heating and cooling

The change of seasons necessitates alternate heating and cooling systems, which are indispensable for nearly a third of the global population. Integrating latent thermal energy storage (LTES) and heat pumps...

Performance analysis of cross seasonal thermal storage solar soil source heat pump drying system

Performance analysis of cross seasonal thermal storage solar soil source heat pump drying system

Equivalent combined cycle modeling and performance optimization for a three-heat-reservoir thermal Brownian heat transformer with external heat-transfer

Three-heat-reservoir (THR) heat transformers can upgrade temperature gradient of thermal energy, and lots of instructive research has been conducted in the last decades. However, study of THR heat transformer cycle theory in micro systems remains lacking. By employing macro equivalent combined cycle method, this paper builds a finite-time thermodynamic model of THR thermal Brownian heat transformer, which is a combination of a two-reservoir thermal Brownian heat pump driven by a two-reservoir thermal Brownian engine. Expressions of performance parameters are deduced, and operating temperatures and external load ratio are determined by solving heat balance equations. Maximal heating load and corresponding coefficient of performance (COP) are given by modulating external load, heat exchanger inventory allocations and barrier height synchronously, and the optimal thermal conductance allocations and optimal working temperatures are identified. Results indicate that external thermal resistances affect heat flow transmission and the coupling of combined cycle, ultimately shaping the cycle performance. Half of the overall heat exchanger inventory should be arranged in middle heat exchanger under maximal heating load objective. Heating load exhibits an extremum with respect to COP. Equivalent combined cycle modelling is an effective and efficient method for performance optimization of THR thermal Brownian heat transformers with external heat-transfer.

Experimental study of a novel design bi-fluid based photovoltaic thermal (PVT)-assisted heat pump dryer

This study evaluated the performance of a novel design bi-fluid (air and refrigerant)-based photovoltaic thermal assisted heat pump dryer (BfPVTA-HPD), combining a compact bi-fluid PVT using curved directional fins that direct air at different points to the evaporator/waste aluminum material and HP system with a PVT air outlet mounted micro-channel condenser. BfPVTA-HPD was analyzed regarding energy, exergy, and drying characteristics at two different times, in clear and partially cloudy weather conditions. Mint leaves (Mentha piperita L.) were dried to evaluate BfPVTA-HPD's drying capabilities. The average electrical, thermal, and exergy efficiencies of PV and PVT for Exp-1 and Exp-2 varied to 15.97, 16.54 %, 18.21, 18.23 %, 55.36 %, 42.04 %, 30.95 %, and 25.08 %, respectively. In Exp-1 and Exp-2, respectively, while an increase of 12.32 % and 9.29 % in the average electrical efficiency was achieved by using PVT, an average of 3.15 and 2.86 were reached in the coefficient of performance (COP) of the heat pump. The exergy indicators (the improvement potential, sustainable index, and waste exergy ratio) for the Exp-1 are 839.52, 1.39, and 0.82. The exergy indicators for the Exp-2 are 1166.14, 1.30, and 0.84, respectively. The experiment's average mass transfer coefficients were obtained as 1.17 × 10−8 and 7.75 × 10−9 m/s respectively. The experiment's average effective diffusivity coefficients were obtained as 2.90 × 10−11 and 2.04 × 10−11 m2/s, respectively. The recommended BfPVTA-HPD can be used as a new model to improve the ecological footprint and green manufacturing. Furthermore, the electricity and heat production required for the sustainability of the drying system in spring and winter can be realized.

Operation study of the photovoltaic thermal heat pump integrated energy system under trigeneration condition and harsh conditions

In recent years, the photovoltaic thermal heat pump has gained significant attention as a near zero-carbon energy technology, due to the comprehensive ability to provide heating in winter, cooling in summer, photovoltaic power generation and domestic hot water throughout the year. However, owing to the incomplete research on the system operating characteristics in trigeneration condition and harsh conditions, the production performance and operational stability of the photovoltaic thermal heat pump were not widely recognized. In view of the above problems, the following studies were conducted in this paper: First, the integrated energy system based on the modular photovoltaic thermal heat pump was designed and constructed. Then, the system operation in severe hot and cold season was carried out and the operational stability of the system under harsh operating conditions was demonstrated sufficiently. Afterwards, the operation of the system under the continuous trigeneration operation were analyzed. During the 7-day trigeneration operation, the average hot water output was 12.12 tons and the average photovoltaic power generation was 88.5 kWh in the daytime heating operation. Besides, the average coefficient of cooling performance was 2.32 in the nighttime cooling operation and the effective cooling-supply time of the system was approximately 4 h.

Power system benefits of simultaneous domestic transport and heating demand flexibility in Great Britain’s energy transition

The increasing share of variable renewables in power generation leads to a shortage of affordable and carbon neutral options for grid balancing. This research assesses the potential of demand flexibility in Great Britain to fill this gap using a novel linear optimisation model PyPSA-FES, designed to simulate optimistic and pessimistic transition pathways in National Grid ESO Future Energy Scenarios. PyPSA-FES models the future power system in Great Britain at high spatiotemporal resolution and integrates demand flexibility from both smart charging electric vehicles and thermal storage-coupled heat pumps. The model then optimises the trade-off between reinforcing the grid to align charging and heating profiles with renewable generation versus expanding dispatchable generation capacity. The results show that from 2030, under optimistic transition assumptions, domestic demand flexibility can enable an additional 20–30 TWh of renewable generation annually and reduce dispatchable generation and distribution network capacity by approximately 20 GW each, resulting in a total cost reduction of around £5bn yearly. However, our experiments suggest that half of the total system cost reduction is already achieved by only 25% of electric vehicles alone. Further, the findings indicate that once smart electric vehicle charging reaches this 25% penetration rate in households, minimal benefits are observed for implementing smart 12-hour thermal storages for heating flexibility at the national level. Additionally, smart heating benefits decrease by 90% across all metrics when only pre-heating (without thermal storages) is considered. Spatially, demand flexibility is often considered to alleviate the need for north–south transmission grid expansion. While neither confirmed nor opposed here, the results show a more nuanced dynamic where generation capacities are moved closer to demand centres, enhancing connectivity within UK sub-regions through around 1000 GWkm of additional transmission capacity.

Transient modeling of stratified thermal storage tanks: Comparison of 1D models and the Advanced Flowrate Distribution method

Thermal energy storage (TES) is one of the key technologies for enabling a higher deployment of renewable energy. In this context, the present study analyzes the modeling strategies of one of the most common TES systems: stratified thermal storage tanks. These systems are essential to many solar thermal installations and heat pumps, among other clean energy technologies. Three different one-dimensional tank models are compared by their computing speed and resilience to long time steps. Two of the models analyzed are numerical, one being explicit and the other one implicit, and the other is analytical. The models are validated against data from experiments carried out considering small-scale stratified tanks, showing that their performance can be improved by using the Advanced Flowrate Distribution (AFD) method. The results show that the analytical model maintains its accuracy with longer time steps and is robust against divergence. Conversely, the numerical models show equivalent performance for short time steps, while the computation time is reduced. Although the AFD method shows promising results by achieving an improvement of 43% in terms of Dynamic Time Warping, its parameter optimization must be generalized for different tank designs, flow rates, and temperatures.

Thermo-Mechanical Jitter in Slender Space Structures: A Simplified Modeling Approach

Thermally induced vibrations usually affect spacecraft equipped with light and slender appendages such as booms, antennas or solar panels. This phenomenon occurs when a thermal shock, resulting from the sudden cooling and warming phases at the entrance and exit from eclipses, triggers mechanical vibrations. The study proposed hereafter concerns the modeling and prediction of jitter of thermal origin in a long and thin plate with a sun-pointing attitude in geostationary orbit. The system’s temperature and dynamics are described by a set of equations expressing the two-way coupling between the thermal bending moment and the shape of the panel. The structure is discretized and reduced to a one-degree-of-freedom simplified model able to identify a mechanism of thermal pumping that could lead to instability. Finally, the results of the analysis are compared with those obtained with a more accurate FEM modelization.

Thermal and Coherent Spin Pumping by Noncollinear Antiferromagnets.

Antiferromagnets attract much interest because of their potential for spintronic applications and open fundamental physics questions, but especially noncollinear antiferromagnets remain relatively unexplored. Here, we formulate the thermal and coherent pumping of spins in noncollinear antiferromagnets|normal metal bilayers. We find that the spin current polarization is a vector with components along both the Néel vector and net magnetic moment. The spin mixing conductance for the coherent spin pumping is a tensor with elements depending on the degree of noncollinearity and interface spin configuration. We explain the controversial sign problem of the antiferromagnetic spin Seebeck effect by interface effects and suggest that interface engineering may enhance the spin pumping efficiency.

Parameter optimization of hot dry rock heat extraction based on discrete element crack network model

Hot-dry-rock (HDR) has long been considered a potential exploitable energy source due to its high energy content, cleanliness, and abundant reserves. However, HDR typically resides in ultra-deep strata with high temperatures and pressures, which makes its extraction a highly complex thermal-hydrological-mechanical (THM) coupling. In this paper, the THM coupling relationship in the geothermal extraction is clarified. It establishes a dynamic porosity and permeability model and creates a pair-well geothermal extraction model. The investigation focuses on understanding the influence of the pressure difference between pair-wells, number of cracks, and injection temperature on the heat extraction temperature, permeability ratio, geothermal reservoir reduction rate, and heat extraction temperature. The research findings indicate the following: (1) Increasing the inter-well pressure difference from 2 to 10 MPa reduces the extraction temperature from 155 to 138 °C. However, the thermal reservoir permeability ratio increases from 1.07 to 1.35. Consequently, the extraction efficiency rises from 6.2 to 12.4 MW. (2) The number of cracks from 200 to 400 led to a decrease in extraction temperature from 160 to 115 °C. However, the thermal reservoir permeability ratio increases from 1.12 to 1.35. In the first 8 years of extraction, the thermal pumping power of 400 cracks exceeded 200 cracks, but later this trend reversed. (3) Elevating the injection temperature from 20 to 60 °C increases the extraction temperature from 142 to 158 °C while reducing the permeability ratio from 1.28 to 1.20. Consequently, the extraction power decreases from 8 to 6 MW. (4) The inter-well pressure difference has the greatest impact on the decrease in extraction temperature, whereas the number of cracks has the greatest impact on the increase in permeability ratio. Injection temperature has the most significant impact on extraction power. This study reveals that increasing the pressure difference between wells, increasing the number of cracks, and lowering the injection fluid temperature will enhance geothermal extraction power. These findings provide valuable insights for geothermal development.

DATAWARE AND SOFTWARE OF THE AUTOMATED TECHNOLOGY FOR COMPUTER- INTEGRATED CONTROL OF HEAT PUMP SYSTEMS

The paper has solved a scientific and applied problem as for substantiating requirements to technical and functional characteristics of the automated technologies of computer-integrated control of heat pump systems in the heating and cooling modes owing to its dataware and software developing and testing. Following functional procedures have been taken into consideration during the dataware and software development of the computer-integrated subsystem for heating of buildings: monitoring of ambient air temperature, ground temperature, and operating modes of functional elements of the heat pump system as well as zonal monitoring of indoor air temperature; computer-integrated processing of the monitoring data; automated control of the heat pump as well as modes of zonal thermal medium supply to the building; and analysis of energy efficiency as for implementation of the proposed computer-integrated method to control systems of thermodynamic heating. It has been identified that thermal capacity of a heat pump is rather sensitive to indicators of the total heat losses of a building. If the total heat losses increase from 0.2°С/hour up to 0.5°С/hour then constant value of the thermal capacity increases by 48%. Moreover, thermal capacity of a heat pump is quite sensitive to ambient air temperature dynamics: if temperature variation is 12°С (i.e. 3°С-9 °С) then average increase in thermal capacity is 58 %. Following functional procedures have been involved during the dataware and software development of the computer-integrated subsystem for cooling of buildings: monitoring of ambient air temperature and operating modes of functional elements of the heat pump system; zonal computer-integrated monitoring of indoor air temperature; computer-integrated the monitoring data processing based upon microcontrollers; automated control of the thermal pump operating modes (i.e. heat energy outfeed and release to the main intercooler unit); and analysis of energy efficiency as for implementation of the proposed computer-integrated method to control systems of thermodynamic cooling of buildings. The abovementioned has helped identify that thermal capacity of a heat pump is rather sensitive to indicator of heat exchange with surrounding air: four times increase in heat-exchange coefficient (i.e. from 1°С/hour up to 4°С/hour) results in 20% growth of thermal capacity of the cooling subsystem system at similar ambient air temperature (it varies from 30°С up to 36 °С) if the maintained target indoor temperature is 22°С.

Integration of solar thermal collectors and heat pumps with thermal energy storage systems for building energy demand reduction: A comprehensive review

Solar energy, coupled with innovative technologies, holds the promise of propelling buildings towards net-zero and carbon neutrality. In this regard, this review explores the integration of solar technologies, heat pumps, and thermal energy storage systems to reduce building energy demand. It thoroughly examines various types of solar thermal collectors (STCs), including both concentrating devices like compound parabolic concentrators and parabolic troughs, as well as non-concentrating designs such as flat plate and evacuated tube collectors. It examines innovative strategies for enhancing STC performance, such as alternative profiles for compound parabolic concentrators and the insertion of thermal fins in absorber tubes. Furthermore, the review categorizes solar-assisted heat pumps (SAHPs) into indirect expansion (IDX) and direct expansion (DX) systems, describing their advantages and limitations. It performs a comparison between IDX-SAHPs and DX-SAHPs, explaining their effectiveness and applicability. Eventually, the review explores thermal energy storage materials, categorizing them into sensible heat storage, latent heat storage, and thermochemical heat storage (TCHS). It discusses the advantages and disadvantages of each category, as well as notable materials within them. A comparative examination between open and closed systems for TCHS further enriches the discussion. Throughout the review, recent advancements and key findings from relevant studies are summarized in separate tables, offering valuable information into practical strategies for sustainable building energy systems. Regarding the provided sections, this review plays a crucial role in introducing scholars to practical methods employed in recent years to integrate the STCs with heat pumps and thermal energy storage systems.

Entangled two-photon quantum heat engine: Dissipative nonequilibrium dynamics and correlated statistics

Recently, the thermodynamics of open quantum systems driven by light fields has been investigated in the framework of quantum heat engines, whose output work can be measured as a spectroscopic signal. In this work, we investigate a four-level quantum heat engine that generates cascaded entangled photon pairs, treating the hot bath as an incoherent thermal pump and focusing on the correlation statistics of the output work and photon indistinguishability. We show that the dissipative nonequilibrium dynamics of this thermodynamic open quantum system can be reconstructed by correlation measurements under carefully mediated optical control. Comparing our findings with the traditional coherently pumped model, we find that the thermal pumping has the potential to generate nonclassical correlations resulting in photon indistinguishability, displaying an advantage in probing the nonequilibrium effects induced by the baths at different temperatures. Our work also demonstrates that incoherent pumping can optimize such correlations in output work beyond the classical limit. Lastly, we show that nonclassical correlations and resonant power at steady state cannot be simultaneously maximized in the weak coupling regime. Published by the American Physical Society 2024

Examination of Operational Methods for a Low-Temperature Aquifer Thermal Storage Air Conditioning System Based on Operational Performance and Considerations of Thermal Storage and Pumping Volume Balance

Aquifer Thermal Energy Storage (ATES) systems are garnering attention as high-efficiency air conditioning technologies that contribute to the realization of a carbon-neutral society. This study focuses on an ATES system constructed in Japan, characterized by its complex geological conditions and thin aquifer layers. Detailed actual performance data measured over four years are presented, and performance analysis results show that a COP of 5 was achieved for the overall building cooling and heating system. In addition, the study provides a detailed analysis of the imbalance in heat quantity, remaining heat storage, and other factors based on actual data, identifying operational issues and summarizing specific improvement measures. Finally, as a proposal for a sustainable operational method to balance the cumulative heat storage and pumping volume of cold and hot water, specific operational procedures are summarized, including setting the return water temperature for the next season based on the dimensionless average pumping temperature of the previous season, and a flowchart is presented. There is no prior research that shows such specific operational procedures, and this can be considered an important achievement of this study.

Systems and Methods for Transformation and Degradation Analysis.

Modern concepts in irreversible thermodynamics are applied to system transformation and degradation analyses. Phenomenological entropy generation (PEG) theorem is combined with the Degradation-Entropy Generation (DEG) theorem for instantaneous multi-disciplinary, multi-scale, multi-component system characterization. A transformation-PEG theorem and space materialize with system and process defining elements and dimensions. The near-100% accurate, consistent results and features in recent publications demonstrating and applying the new TPEG methods to frictional wear, grease aging, electrochemical power system cycling-including lithium-ion battery thermal runaway-metal fatigue loading and pump flow are collated herein, demonstrating the practicality of the new and universal PEG theorem and the predictive power of models that combine and utilize both theorems. The methodology is useful for design, analysis, prognostics, diagnostics, maintenance and optimization.

Optimising liquid impingement jet arrays for concentrated heat sources

This work seeks to investigate jet array impingement liquid cooling of CPU processors that utilise Integrated Heat Spreaders. In this study, single and centralised heat sources of various sizes (10 mm to 20 mm) were investigated, and a series of single and multi-objective optimisation studies were carried out to determine the optimum arrangement of microjets for different heat source sizes based on variable geometric inputs of the jet orifice plate. The results indicated that the design of the optimum jet orifice strongly depends on the size of the heat source as well as whether the target optimisation strategy is to achieve minimum thermal resistance, or both minimum thermal resistance and minimum pumping power simultaneously. A clustering of quite different orifice designs in optimal zones is observed, where approximately the same hydraulic and/or thermal performance is observed.

Feasibility and performance study on the novel photovoltaic thermal heat pipe/heat pump composite cycle trigeneration system in summer

Photovoltaic thermal heat pump technology with deep utilization of solar energy has great market potential to achieve “Carbon Neutrality” in the building sector. A novel photovoltaic thermal heat pipe/heat pump composite cycle trigeneration system synergetic driven by a compressor and a working fluid circulating pump was proposed and experimentally verified. On this basis, the trigeneration performance and operating characteristics of the novel system were tested and investigated in the summer. The experimental results showed that the novel system can arbitrarily switching between different cycles and has an excellent energy saving effect. The average electrical efficiency, thermal efficiency, heating COP, and refrigerating COP of the novel system were 10.1%, 40.3%, 7.02, and 2.60, respectively. During the whole day, the comprehensive COP for heating, power generation, and refrigerating of the novel system was 13.93. The heating COP and comprehensive COP of the novel system were 20%–50% and 40%–65% higher than that of the existing photovoltaic thermal heat pump trigeneration system, respectively. Furthermore, the CO2 emission of the novel system was 4042 kg CO2 in summer, which was 20%–80% lower than that of other technical solutions. The novel system represents a practical response to the need to achieve the total decarbonization of the building sector.