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The purpose of the research was to examine the savings potential and verify how to reduce the energy consumption in new hospitals by about 50%. Our results are also very relevant in other buildings complex with surplus heating, cooling and thermal storage. Conversion and utilization of surplus heat sources represent well known technologies and are under constant development. In large building complexes there is a potential for coordinated production, storage, and distribution of energy. Heat pump, chiller and thermal storage technologies enable re-use of surplus heat/cool energy throughout the year. Energy supply and demand are typically modelled with separate tools and timescales. Through our study new methods are developed for operation of interacting simulating models. These methods provide tools to step into optimization of combinations of integrated energy systems. The main issues focus on hydraulic water flow and storage systems as a basis. The layout is important not only with regards to utilize the energy quality, i.e. the temperature. In addition, control strategies are shown to have a highly relevant impact on the possible savings. Some details of new hydraulic layout and control design will be described and discussed in the paper. Both in combination with heating, cooling and storage system. Our research indicates that it is possible to save between 20-50% of the energy consumption with optimizing the technical installations in Oslo area. Another benefit of integrated thermal modelling is to reduce the risk of permafrost in ground source heat pump installations. This risk is relevant for large buildings in northern Norway, at annual mean temperatures are below 0̊C. This paper shows how integrated simulation and design can be used to avoid permafrost. [ABSTRACT FROM AUTHOR]

Abstract: Due to the unique properties of near-critical fluid, trans-critical/supercritical CO2 based natural circulation loop (NCL, or thermosyphon) has been proposed in many energy conversion systems, such as solar heater, waste heat recovery, next generation nuclear cooling, etc. This paper presents an experimental investigation of a near-critical CO2 thermosyphon. The closed thermosyphon is specially designed for high pressure experiments, where natural convection is achieved only by heating and cooling of fluid in the loop. The system is operated in wide range of pressures from around 6.0 to 15.0MPa in the near-critical region. It is found that the NCL flow will change from unstable sub-critical two-phase flow to stable liquid flow, and then become stable supercritical circulation with the increase of system initial pressure. The heat transfer behaviors are analyzed for stable flow conditions mainly for supercritical region. General variations of the fluid temperature, mass flow rate and loop pressure are presented in this paper. In the steady supercritical region, the heat transfer performance of the cooler show very small changes with bulk mean fluid temperature, and at the heater better heat transfer is found for conditions close to the pseudo-critical point. The heat transfer dependency on operation pressure and evolution mechanisms are also discussed in detail in this paper. [Copyright &y& Elsevier]

Highlights • A two-phase flow visualisation and heat transfer experiment bench was established. • Flow patterns at various crank angles in an open cooling gallery were captured. • The effects of motor speed and heating on flow patterns were discussed. • The temperature distribution was obtained and the effect of speed was discussed. • Transition from laminar flow to turbulent flow has been identified. Abstract The demand of increasing power density of the Internal Combustion Engine promotes the technology development using internal cooling gallery of the piston. The oil flow and heat transfer performance of the piston internal cooling gallery have great influence on the cooling performance, which affects the thermal conditions of the piston and of the entire engine. The experimental study using visualising method is therefore critical and important to observe the flow patterns inside the piston gallery. In this paper, we presented the visualised study of two-phase flow patterns within an open cooling gallery by using a high-speed camera at various crank angles. The effects of motor speed both on the flow patterns and temperature distribution were investigated and the heat transfer mechanisms in gas-liquid two-phase flow during reciprocating motion were explored. Based on the study, the period-doubling phenomenon, which represented the transition from laminar flow to turbulent flow, was observed when the speed was around 400–500 rpm. Results indicated the increase of motor speed can effectively improve the cooling performance. Results also showed when the speed was higher than 600 rpm, the reduction of temperatures was quite close, which proven the existence of optimal or minimum requirement of motor speed to achieve good quality cooling performance. The results obtained in this study could be used as a critical reference for numerical studies and important experimental reference to further investigate the design and optimisation of engine cooling gallery for vehicle application. [ABSTRACT FROM AUTHOR]

• Building integrated earth-to-air heat exchanger for global footprint reduction. • Offering similar energy gains than traditional earth-to-air heat exchanger. • Two time-dependent 3-dimensional finite volume models are developed and coupled. • Coupled heat and moisture transfers and complex boundary conditions are considered. • Successful validation against in-situ temperature and water content measurements. This paper investigates an innovative earth-to-air heat exchanger (EAHE), namely the geothermal foundation Fondatherm®. This system solves numerous technical problems inherent to a traditional EAHE. However, an accurate understanding of its thermal behavior is crucial to ensure the best energy gain and its economic viability. This current paper focuses on a numerical study of the ventilated foundation. A time-dependent three-dimensional finite volume numerical model is developed. This model considers coupled heat and moisture transfers as well as complex boundary conditions such as the weather, the building and the water table simultaneous influences. A matric-head based system of equations is used to represent the heat, vapor and liquid transfers within the soil. It is combined to a capillary pressure-based formulation of the heat and vapor balance equation for the concrete foundation. Furthermore, a numerical method built on a switching from a potential- to a flux-based system of equations is proposed. It is added to a variable time-step method of resolution and allow to handle the greatest hygric loads variations at the ground surface. The numerical code is successfully validated against analytical solutions for simple cases, and against experimental and in situ measurements. [ABSTRACT FROM AUTHOR]

Latent heat thermal energy storage is an attractive technique as it can provide higher energy storage density than conventional heat energy storage systems and has the capability to store heat of fusion at a constant (or a near constant) temperature corresponding to the phase transition temperature of the phase change material (PCM). This paper provides a state-of-the-art review on phase change materials (PCMs) and their applications for heating, cooling and electricity generation according to their working temperature ranges from (−20 °C to +200 °C). Four working temperature ranges are considered in this review: (1) the low temperature range from (−20 °C to +5 °C) where the PCMs are typically used for domestic and commercial refrigeration; (2) the medium low temperature range from (+5 °C to +40 °C) where the PCMs are typically applied for heating and cooling applications in buildings; (3) the medium temperature range for solar based heating, hot water and electronic applications from (+40 °C to +80 °C); and (4) the high temperature range from (+80 °C to +200 °C) for absorption cooling, waste heat recovery and electricity generation. Different types of phase change materials applied to each temperature range are reviewed and discussed, in terms of the performance, heat transfer enhancement technique, environmental impact and economic analysis. The review shows that, energy saving of up to 12% can be achieved and a reduction of cooling load of up to 80% can be obtained by PCMs in the low to medium–low temperature range. PCM storage for heating applications can improve operation efficiency from 26% to 66%, depending on specific applications. Solar thermal direct steam generation (DSG) is the most common electricity generation application coupled with PCM storage systems in the high temperature range, due to the capability of PCMs to store and deliver energy at a given constant temperature. The recommendations for future research are also presented which provide insights about where the current research is heading and highlights the challenges that remain to be resolved. [ABSTRACT FROM AUTHOR]

The melting process and the solidifying process of phase change material (PCM) are usually considered symmetrical in the traditional PCM heat transfer models, but there are inevitable calculation errors using these models. In this paper, a new heat transfer model of PCM based on the energy asymmetry was built, and it was validated by experimental data. It was found that the two main reasons for the energy asymmetry of the PCM were the melting temperature range and the solidifying temperature range were not the same and the supercooling problem during the cooling process. No matter for only one thermal cycle or for the multiple thermal cycles, the results from the asymmetrical model and the symmetrical model were different. Apparently, compared with the symmetrical model, the asymmetrical model had higher accuracy, and the heating/cooling process in the asymmetrical model was more consistent with the real heating/cooling process of the PCM. [ABSTRACT FROM AUTHOR]

Prepreg compression forming(PCF) is well known for the manufacturing process with high mechanical properties, low equipment cost and high surface quality. Generally, the temperature difference and rapid heat transfer between the tool and laminate can lead to some problems such as heat distortion, low formability and bad surface quality. Therefore, this paper attempts to solve these problems by using the rapid heating and cooling device, similarly to injection molding. It is possible to heat the tool above T g and cool it down under T g within few minutes. Also, the defect of distortion is prevented by rapid cooling system. In this study, the manufacturing process of CFRTP B-pillar reinforcement was designed based on structural analysis and thermal forming analysis. First, the thickness of laminate satisfying the energy absorption of conventional steel product was determined through structural analysis. Second, the thermal properties of the prepreg was evaluated for the thermal forming analysis. The thermal forming analysis of CFRTP laminate was carried out to determine the holding force. Finally, B-pillar reinforcements of CFRTP were fabricated and evaluated their dimensional accuracies and shear angle. [ABSTRACT FROM AUTHOR]

• A new methodology to investigate the impact of thermal mass is defined. • The use of unrepresentative boundary conditions could lead to inaccurate conclusions. • High thermal mass helps to decrease and regulate the internal temperature. • High thermal mass could increase energy use in the summer and winter seasons. • Isolating thermal mass through internal insulation results in better energy performance than external insulation. Contradictory conclusions have been reported on whether thermal mass reduces or increases energy demand in hot and cold climates. A novel approach to measuring the impact of thermal mass on the building's energy consumption is presented. The method aims to better represent reality and applies two different control conditions simultaneously in a numerical model: the first condition, which has been used in past studies, adjusts the internal boundary condition based on the time duration of heating/cooling activation (simulating an occupancy pattern) and the second, which has not been used in past studies, adjusts the internal boundary condition based on both the time duration and the internal temperature (simulating an occupancy pattern and the thermostatic control system). When investigating the impact of thermal mass on the internal temperature in a scenario where no heat is transferred into the building, the high thermal mass outperforms the low thermal mass, showing a time-shifting effect, long time lag, and small decrement factor. However, when modelled using the method presented in this paper, high thermal mass results in greater energy consumption during summer and winter periods in Saudi Arabia. During transition seasons where temperature swings occur on either side of the indoor set-point temperatures, thermal mass reduces thermal transmission. The impact of thermal mass is also investigated for several climatic conditions in Saudi Arabia. Simulation results show that an internally exposed thermal massive wall section results in greater energy consumption when compared to a similar building with isolated thermal mass (i.e. insulated internally). This is due to the fact that even though the internal temperature inside the building is being cooled/warmed up to the set-point, the thermal mass continues to transfer heat that is absorbed by the building's fabric from/to the interior, placing a greater demand on the cooling/heating system. Over the course of a year, however, the impact of thermal mass is negligible when compared to other factors, such as the insulative properties of the building's fabric. [ABSTRACT FROM AUTHOR]

Abstract: Thermal mass can be effectively used for controlling temperature in buildings. Based on its location and function, building thermal mass can be classified as interior thermal mass and exterior (envelope) thermal mass. In this paper, the dynamic heat transfer performance of exterior Planar Thermal Mass (ePTM) subject to sinusoidal heating and cooling is investigated. When the mean value of outdoor air temperature is equal to indoor air temperature, solutions of temperature distribution and heat flux in ePTM are deduced analytically. Using the analytical solutions, heat exchange and thermal storage of ePTM are attained. Correspondingly, the time lag and the decrement factor are obtained; they show similarity characteristics—independent of environment temperatures. When the two temperatures are not equal, an approximated temperature distribution solution is developed based on the principle of superposition, which has been validated by numerical solutions. The approximated solution is then used to investigate the heat exchange between the ePTM and the environment. In contrast to the common belief that a large thermal mass has an apparent insulating effect, no “insulating effect of mass” under sinusoidal heating and cooling is found in this investigation. Another two rules of thumb based on common belief are corrected: a wood wall is better than a concrete wall of same thickness as exterior walls in terms of the time-lag effect and the decrement factor. The effect of the time lag is not the longer the time lag is the better its contribution to thermal comfort becomes. [Copyright &y& Elsevier]

Abstract: New Zealand has a temperate maritime climate. Despite mild winters compared to nations with continental climates, New Zealand houses have been reported to often be at temperatures below internationally recommended levels. Sources of additional heating are therefore of interest to many New Zealand home occupants. Roof space solar gains have been identified as one possible source of heating. This paper investigates the energy gains available in New Zealand homes from ventilation systems drawing air from the roof cavity. Three New Zealand houses were monitored and a computer-based thermal building simulation developed to quantify the heating and cooling energy that might be transferred by home ventilation systems. The computer model simulating the temperature in the roof space and occupied spaces was constructed using MATLAB, and used publicly available weather station data as the inputs. A good match between measured and modelled results was obtained. Small heating and cooling benefits are possible at certain times from pumping roof space air into the living areas of some New Zealand houses. The magnitude of these benefits, however, is not significant compared with the space heating required to maintain reasonable indoor temperatures over the New Zealand winter. [Copyright &y& Elsevier]

Abstract: The study of heat transfer in the entrance region of ducts with different cross-sections is important in engineering practice. This paper considers laminar, hydrodynamically fully developed flow in the thermal entrance regions of rectangular passages, emphasizing heat transfer aspects. By having a prescribed heating or cooling rate and considering the wall temperature to depend on the axial coordinate alone, the temperature solution leads to an integral equation. Solution of this equation is found using an inverse technique to determine the temperature at the walls. For verification purposes, an asymptotic solution is developed which produces results that agree very well with those from the inverse analysis. The results include a correlation and computed values of the Nusselt number at entrance locations, for rectangular ducts with different aspect ratios. [Copyright &y& Elsevier]

• Effect of tilt and length on porous miniature heat pipes thermal performance is investigated experimentally. • Thermal resistance network of 1D of miniature heat pipes with fin is detailed for thermal modelling. • Prediction of evaporation and condensation heat transfer coefficients using experimental results. • Effect of adiabatic length on capillary pressure of the two studied heat pipes using the developed hydraulic model. • Effect of porous media parameters on thermal resistance and heat pipes thermal performance and evaluation of optimal porosity. Miniature heat pipes are considered as an innovative solution able to dissipate high heat fluxes with low working fluid charge, temperature control, and operating with minimum energy consumption and less noise. In this paper, results show that tilt ranging [10°:60°] has not an impact on heat transfer meanwhile the system thermal resistance is the lowest at horizontal position. A theoretical analysis on heat pipe thermal performance has been carried out based on experimental data by predicting heat pipe evaporation and condensation heat transfer coefficient. The measured heat transfer coefficients are close to the predicted results with a mean deviation less than 10%. A hydraulic mathematical model is developed and shows a good agreement with Kaya's study using water as working fluid. This work comprises a parametric study that investigates the effect of particles size, porosity, permeability, heat pipe length on heat transfer and capillary pressure. The obtained results show that the heat pipe operating temperature rises when particles size increases from 1 μ m to 90 μ m and the optimum porosity range is between [10%–40%]. [ABSTRACT FROM AUTHOR]