Showing papers on "Heat exchanger published in 2015"
TL;DR: In this paper, the authors provide a critical review of the analysis of heat transfer by borehole and foundation pile ground heat exchangers with an emphasis on different analytical models, including heat-source models, short-time models, models for energy piles, in situ thermal-response tests, indoor sandbox experiments, and parameter estimation as an inverse problem.
237 citations
TL;DR: In this paper, the authors reviewed the applications of ANN for thermal analysis of heat exchangers and highlighted the limitations of ANN in this field and its further research needs in the field.
232 citations
TL;DR: In this paper, a review of micro-and minichannel heat exchangers as heat sinks and heat exchanger has been presented, and the persisting lacunae of this technology drawn from the review have been pointed out.
Abstract: Depleting energy resources have become the driving force for their conservation. Increasing the system efficiencies is one method by which sustainability of energy may be ensured, for which miniaturization has successfully provided solutions. Miniature heat exchangers, owing to their high thermal performance, have the potential to provide energy efficient systems. In addition, their characteristics of compactness, small size and lesser weight have attracted widespread applications. Various works on micro- and minichannel heat exchangers as heat sinks and heat exchangers have been reviewed in this paper. Currently employed fabrication techniques and different applications have been summarized. An overview of the single-phase thermo-hydraulic studies in micro- and minichannel heat sinks has been presented. Literatures related co-current, counter-current and cross-current micro- and minichannel heat exchangers have been discussed. Finally, the persisting lacunae of this technology drawn from the review have been pointed out.
229 citations
TL;DR: In this paper, the authors present an updated review of properties of nanofluids, such as physical (thermal conductivity) and rheological properties, with emphasis on their heat transfer enhancement characteristics.
229 citations
TL;DR: In this paper, water-based nanofluids have been used to enhance the heat transfer performance of a car radiator by adding ZnO nanoparticles to base fluid in different volumetric concentrations (0.01, 0.08), 0.2% and 0.3%).
226 citations
TL;DR: In this article, a review of the development of the mathematical and numerical analysis procedures, development of hardware and test procedures, and validation of the results is presented, with a historical perspective, going as far back as Lord Kelvin's treatment of transient heat conduction problems.
Abstract: When designing ground heat exchangers used with ground source heat pump systems, a critical design property is the thermal conductivity of the ground. Thermal response tests are used to measure the site-specific thermal conductivity and are also used to measure the thermal resistance of a borehole heat exchanger as installed. Thermal response tests are commonly used today for design of multiple borehole ground heat exchangers, where knowledge of the ground thermal properties can help avoid undersizing of ground heat exchangers, leading to poor system performance, and oversizing of ground heat exchangers, leading to overly costly systems. This review covers the development of the mathematical and numerical analysis procedures, development of the hardware and test procedures, and validation of the results. We take a historical perspective, going as far back as Lord Kelvin's treatment of transient heat conduction problems in the 1880s, further development of which allowed analysis of conductivity measurements from transient needle probes by the 1950s. We focus on development of test rigs and test procedures in the 1980s and 1990s and validation of the measurements. More recent developments are covered throughout the review.
209 citations
TL;DR: The thermal network approach is a robust engineering tool that is easy to implement and program, is user friendly, straightforward, computationally efficient, and serves as a baseline methodology to produce results of reasonable accuracy.
198 citations
TL;DR: In this article, a numerical model of an Adiabatic compressed air energy storage (A-CAES) system with packed beds and validated it against analytical solutions is presented.
193 citations
TL;DR: In this paper, eight full-scale energy foundations were constructed for a new building at the US Air Force Academy and three of the foundations were instrumented with strain gages and thermistors, and their thermo-mechanical response during a heating and cooling test was evaluated.
Abstract: Eight full-scale energy foundations were constructed for a new building at the US Air Force Academy. The foundations are being used to demonstrate this technology to the United States Department of Defense and have several experimental features in order to study their thermal–mechanical behavior. Three of the foundations are instrumented with strain gages and thermistors, and their thermo-mechanical response during a heating and cooling test was evaluated. For a temperature increase of 18 °C, the maximum thermal axial stress ranged from 4.0 to 5.1 MPa, which is approximately 25 % of the compressive strength of concrete (estimated at 21 MPa), and the maximum upward displacement ranged from 1.4 to 1.7 mm, which should not cause angular distortions sufficient enough to cause structural or aesthetic damage of the building. The end restraint provided by the building was observed to change depending on the location of the foundation. The heat flux per meter was measured by evaluating the temperatures and flow rates of a heat exchanger fluid entering and exiting the foundations. The heat flux values were consistent with those in the literature, and the foundation with the three continuous heat exchanger loops was found to have the greatest heat flux per meter. The transient thermal conductivity of the subsurface measured using the temperatures of the subsurface surrounding the foundation ranged from 2.0 to 2.3 W/mK, which is consistent with results from thermal response tests on energy foundations reported in the literature.
190 citations
TL;DR: In this paper, the authors proposed a biomass combined cooling, heating, and power (CCHP) system that contains a biomass gasifier, a heat pipe heat exchanger for recovering waste heat from product gas, an internal combustion engine to produce electricity, an absorption chiller/heater for cooling and heating and a heat exchange to produce domestic hot water, and the case demonstrated that the energy efficiencies in the three work conditions are 50.00%, 37.77%, and 36.95%, whereas the exergy efficiencies are 6.23%, 12.51%,
177 citations
TL;DR: In this article, the experimental and modeling studies carried out on ground coupled heat exchanger (GCHE) systems are reviewed and compared with ground source heat pump (GSHP) and EAHE systems.
Abstract: The use of ground coupled heat exchanger (GCHE) systems is increasing worldwide. They are mainly used for space conditioning, water heating, agricultural drying, bathing, swimming, etc. They reduce cooling load in summer and heating load in winter. GCHE systems make available excellent scope to conserve significant amount of primary energy and thus mitigating the impact on environment through emission reduction. This paper reviews the experimental and modeling studies carried out on GCHE systems. The reviewed literature focuses on performance of both types of GCHE systems viz. earth–air heat exchanger (EAHE) and ground source heat pump (GSHP) systems and brings out their merits and demerits.
TL;DR: In this paper, a simplified heat exchange model based on the first principle of heat exchange between two media (fluid and rock) and Newton's law of cooling is proposed to model the coupled hydro-thermal system for hot dry rock geothermal applications.
TL;DR: In this article, a 100kW regenerative Brayton heat engine driven by the hybrid of fossil fuel and solar energy was considered for optimization based on multiple criteria, such as power output, thermal efficiency and dimensionless thermo-economic performance.
TL;DR: In this paper, a double-pipe heat exchanger made of corrugated outer and inner tubes was investigated, where both of the inner and outer tubes were made by means of a special machine and the heat transfer coefficient was determined using Wilson plots.
TL;DR: In this article, an extensive review of numerical and experimental studies on heat transfer enhancement, which covers the laminar and turbulent flow regions in the corrugations, especially in corrugated tubes, is presented.
TL;DR: In this paper, the forced convective heat transfer coefficient of a biologically produced nanofluid flowing in a circular tube inside a heat exchanger was investigated and a new correlation was proposed with absolute average deviation of 3.43.
TL;DR: In this article, a novel micro CCHP (combined cooling, heating and power system) driven by solar and geothermal energies is modeled and optimized using NSGA-II to achieve the final solutions in the multi-objective optimization of the system for four working fluids including R134a, R423A, R1234ze and R134yf from the energy, exergy and exergoeconomic viewpoints.
TL;DR: In this article, a dual-loop ORC system consisting of a high temperature (HT) loop and a low temperature (LT) loop for engine waste heat recovery is presented.
TL;DR: In this paper, a dual-loop organic Rankine cycle (ORC) system is designed to recover the waste heat of a diesel engine, where water is selected as the working fluid for the HT loop and wet steam expansion, which can be implemented through screw expanders, is exploited.
TL;DR: In this article, the authors comprehensively review various useful techniques adopted in detail for energy and exergy performance enhancements, and provide the perspectives for researchers and engineers to design more efficient latent TES systems.
Abstract: Latent heat thermal energy storage (TES) can be an efficient option to cater to fluctuating energy demands and at the same time to obtain a higher performance from the energy and exergy aspects. Latent heat TES storage performance is usually influenced by various operating conditions and design parameters during the energy/exergy stored and retrieved. The scope of investigation is to comprehensively review various useful techniques adopted in detail for energy and exergy performance enhancements, and provide the perspectives for researchers and engineers to design more efficient latent TES systems. Various influencing factors can be enlarged to include the heat transfer fluid (HTF) mass flow rate and inlet temperature, phase change material (PCM) melting temperature and number, additives for PCMs, storage unit dimension, heat exchanger surface enhancement, and sensible heating and sub-cooling, etc. The main perspectives and directions including heat transfer mechanism and optimized multiple PCM melting point are provided to enable further research.
TL;DR: In this paper, a parametric investigation of irreversible Stirling heat pump cycles that includes both internal and external irreversibilities together finite heat capacities of external reservoirs is carried out, where three objective functions including the heating load (RH) and coefficient of performance (COP) and thermo-economic criterion (F) have been simultaneously maximized.
TL;DR: In this paper, a detailed analysis of the engines operation is performed to evaluate all thermal streams released by the engines and the thermal matching that maximizes the net power output of the total system composed by engine cooling circuits and ORC cycle is then found by searching for the optimum heat transfer between thermal streams independently of the structure/number of the heat exchangers.
TL;DR: In this paper, the authors presented the comprehensive performance analysis and deduced an easy-to-apply regression model for predicting the cooling capacity of an EAHE, which couples both heat and mass transfer between the air and the tube.
TL;DR: In this article, three types of fin-tube heat exchanger with different surface characteristics were prepared and the effects of the surface characteristic on the frosting and defrosting behaviors of the heat exchangers were investigated experimentally.
TL;DR: In this article, a transient one-dimensional model was developed for studying the thermal performance of EAHE for summer cooling under the Algerian Sahara, where the effect of extremities was also taken into account.
Abstract: A transient one-dimensional model was developed for studying the thermal performance of earth-to-air heat exchangers (EAHE) for summer cooling under the Algerian Sahara. The effect of extremities was also taken into account. The model validation against both theoretical and experimental data of other researchers showed a good agreement. In addition, a detailed sensitive study was carried out in order to investigate the influence of geometrical and dynamical parameters on the thermal performance of EAHE. Results showed that the air outlet temperature decreases with increasing of pipe length but it increases with increasing of pipe cross section and air velocity. However, the daily mean efficiency increases when the length of pipe increases but it decreases when the cross section area of pipe or air velocity increases. It is also observed that the coefficient of performance drops quickly with increasing of air velocity. Considering as reference the thermal performance of EAHE under steady state conditions, the investigation of Derating Factor reveals that the thermal performance of EAHE in transient conditions is more influenced by the variation of operating duration, pipe diameter and air velocity.
TL;DR: In this article, the potential of improving the energy efficiency of a conventional cryogenic air separation unit (ASU) was investigated through modelling and simulation using Aspen Plus v 8.1.
TL;DR: In this paper, the use of genetic and particle swarm algorithms in the design of shell-and-tube heat exchangers is demonstrated, where a cost function (including costs of the heat exchanger based on surface area and power consumption to overcome pressure drops) is minimized.
TL;DR: In this paper, an equivalent thermal circuit is proposed to represent the heat transfer process in a heat exchanger, and then analyzed the temperature variations of all the working fluids in each heat exchange to establish the equivalent thermal circuits for such three basic layouts of HENs as multiple-loop, series, and parallel.
TL;DR: In this paper, a Selective Laser Melting (SLM) was used to fabricate a flat-plate oscillating heat pipe (FP-OHP) with innovative design features, including a Ti-6Al-4V casing and a closed-loop, circular mini-channel consisting of four interconnected layers.
Abstract: Additive manufacturing (AM) allows for layer-by-layer fabrication of complex metallic parts with features typically unobtainable via conventional manufacturing. For heat exchangers, such complex features are desirable for enhancing their heat transfer capability and conformability to specific applications. In this case study, Selective Laser Melting (SLM), a laser-based additive manufacturing process, was utilized to fabricate a compact (5.08 cm × 3.81 cm × 1.58 cm) flat-plate oscillating heat pipe (FP-OHP) with innovative design features, including a Ti–6Al–4V casing and a closed-loop, circular mini-channel (1.53 mm in diameter) consisting of four interconnected layers. Venting holes were integrated to intersect each layer to allow for a unique layer-by-layer, plug-and-pressurize de-powdering procedure. The device channel surface was inspected via Scanning Electron Microscopy (SEM) – and it was found that the channel wall consisted of partially un-melted particles, as well as amorphous melt regions; surface characteristics influential on surface/fluid capillarity and heat transfer. This study also highlights important design and manufacturing concerns encountered during SLM of channel-embedded parts, such as channel surface quality and de-powdering. The Ti–6Al–4V FP-OHP was found to operate successfully with an effective thermal conductivity of approximately 110 W/m K at a power input of 50 W; demonstrating a 400–500% increase relative to solid Ti–6Al–4V.
TL;DR: In this paper, a detailed design and off-design performance analysis based on the preliminary design of turbines and heat exchangers is conducted, and the results indicate that in all considered conditions the designed radial inflow turbine has smooth offdesign performance and no choke or supersonic flow are found at the nozzle and rotor exit.