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Solar district heating systems reduce carbon emissions effectively. Large-scale water pit thermal energy storages (PTES) have high heat capacities, low costs per cubic volume, and long lifetimes. Integrating PTES with a solar heating system can significantly increase solar heating efficiency and alleviate the time and climate constraints of renewable energy. An improved TRNSYS semi-analytical model of PTES (Type 1535–1301) is proposed based on the finite difference method. The model is characterized by discretizing the energy equation and then combining it with the analytical solution of the full differential equation to find the temperature variation. The model is validated with a full year measurement on a Danish PTES. In addition, a parametric investigation of grid discretization, storage geometry, soil properties, and diffuser location is performed. The control strategies are investigated to best utilize the PTES for demand response. The results indicate that the Type 1535–1301 model accurately predicts the year-round thermal performance of the PTES. The differences between the calculated and measured energies are lower than 1.3 %, and the differences between the calculated and measured temperatures are lower than 2.8 K. With an increase of the slope angle of the PTES side wall, the top and side heat losses decrease, and the storage temperature and thermal stratification effectiveness improve. Furthermore, the relative Fourier number (Fo m) is proposed to represent the soil thermal diffusivity. The rise of Fo m leads to an increase of heat loss and a decrease of storage efficiency. The analysis show that the top diffuser is best located at the highest position, and the bottom diffuser is best placed at the lowest position. At the same time, the middle diffuser is best placed at 29 % of the total volume from top to bottom. The semi-analytical model in this paper decreases the annual heat transfer computation time for a single grid to 57 ms. The model has been embedded into TRNSYS for convenient system prediction. The findings of this paper can be used as a reference for engineering practice and subsequent research. [ABSTRACT FROM AUTHOR]

[Display omitted] • The heat exchange performance of an energy pile under different intermittent field operating conditions is compared with that of a borehole heat exchanger. • The thermal impact on the pile concrete and the surrounding soil of the energy pile is characterized. • The differences in heat exchange rates between continuous and intermittent operating conditions for the energy pile are quantified. • The impact of intermittent operating modes of the energy pile on heat transfer efficiency and energy consumption is explored. This paper examines the difference in heat exchange efficiency between an energy pile and a borehole heat exchanger under intermittent operation conditions through a field underground energy structure located in Liyang City, Jiangsu Province, China. Additionally, a 3D finite element numerical model was established to simulate and explore the effect of the intermittent ratio on the heat exchange efficiency of the energy pile under intermittent conditions. This study shows that under intermittent constant power heating, the heat exchange rate per unit pipe length of the energy pile was much higher than that of the borehole heat exchanger. Compared to continuous operation, the average temperature change of the pile body caused by intermittent operation decreased by 59.30%, and that of the soil decreased by 72.90%. Moreover, intermittent operation has the dual advantage of improving heat exchange efficiency and marginally increasing the Coefficient of Performance of the energy pile system, thereby resulting in reduced electrical consumption. By providing field data about the thermal performance of the energy pile and the borehole heat exchanger under intermittent operating conditions, our results contribute to solving the problem of thermal imbalance caused by the long-term continuous operation of energy piles, thereby optimizing the design and operation of heat exchangers and promoting more efficient and sustainable use of geothermal energy. [ABSTRACT FROM AUTHOR]

Highlights • In-situ TRTs were conducted for 48 h with U, 2 U, and W type GHEs. • The ground thermal diffusivity is derived by using an infinite line source model and regression analysis. • The method to derive ground thermal diffusivity from in-situ TRTs was validated with laboratory test results. • An in-situ TRT for W type GHE was numerically modeled by using ground thermal diffusivity and ground thermal conductivity as input parameters. Abstract Ground-coupled heat pump (GCHP) systems are being increasingly utilized in recent years. There are several important parameters in the design of GCHP systems. As ground thermal conductivity is one of the most crucial parameters, it should be measured by conducting in-situ thermal response tests (TRTs). This paper presents the experimental results and analysis of thermal response tests to estimate the ground thermal conductivity and ground thermal diffusivity for three types of ground heat exchangers (GHEs), including U, 2U, and W-type ground heat exchangers (GHEs). Three different types of GHEs were installed in a dredged soil deposit, and continuous TRTs were conducted for 48 h. This study suggests a method to predict ground thermal diffusivity using the infinite line source model from the TRTs. Furthermore, soil samples were collected from different ground layers, and ground thermal properties were measured using laboratory tests. The equivalent ground thermal conductivity and ground thermal diffusivity measured through laboratory tests were compared with the in-situ TRT results that were newly derived in this paper. In addition, ground thermal diffusivity and ground thermal conductivity values that were obtained through research were used as input parameters in numerical analysis. The in-situ TRT results were numerically modeled using the finite element method. [ABSTRACT FROM AUTHOR]

This paper investigates a novel terminal unit that integrates a radiant cooling floor (RCF) with an underfloor air distribution system (UFAD). The unit consists of rectangular modules that are installed above the standard structural floor of the building, creating a raised floor. The upper face of these modules incorporates a grid for easy installation of the pipes of the RCF, while the space between the raised floor and the structural slab is used as the air supply plenum of the UFAD system. The proposed system presents some advantages over the standard air systems: (1) it allows increasing production and zone set point temperatures, which improve the efficiency of the chiller plant, (2) improved comfort, and (3) improved air quality due to reduced mixing within the occupied zone. The proposed system can also solve or mitigate some of the drawbacks of cooling floors: (1) prevent water condensation over the surface of the floor, (2) increase the cooling capacity of the floor, and (3) reduce the response time to changes in the space thermal loads. The interactions between the RCF and the UFAD are not evident. In this paper, the thermal behavior of the combined unit is investigated by means of a numerical model implemented in COMSOL Multiphysics. The accuracy of this model is checked against three experiments undertaken in laboratory using a scale model of the system. In the first experiment, the air above the floor is kept quiescent and the cooling capacity is measured. The maximum relative error between the predicted and measured capacities is 19.5%. The numerical model is then used to study how the air movement within the plenum modifies the transient thermal response of the unit. The second and third experiments are designed to quantify the temperature change of the air circulating within the plenum (thermal decay or TD). In nominal operating conditions, TD is about 2.7 °C. In short, the new terminal unit is like a radiant cooling floor and a UFAD system working separately, but integrated in the same terminal unit. [ABSTRACT FROM AUTHOR]

This paper describes an experimental set-up used to validate predictions from a numerical model for ventilated wall cavity with spray evaporative cooling systems. The validation analysis results have indicated that the numerical model, developed and described in a companion paper, can accurately predict the outlet air temperatures and relative humidity levels achieved by a ventilated wall cavity with a spray evaporative cooling system utilized to air condition buildings in hot and dry climates. Air velocity predictions of the ventilated cavity have been also verified against results obtained from a detailed CFD analysis. Moreover, the experimental testing results indicate that the ventilated wall cavity with an evaporative cooling with 5 μm spray droplets can significantly reduce outdoor air temperatures. Specifically, the system was able to reduce air temperature from 45 °C to 25.5 °C. Moreover, the results of a parametric analysis obtained using the validated numerical solution suggest that there is a significant reduction potential in heat transfer through cavity walls while providing acceptable supply air temperature capable of maintaining indoor thermal comfort. In addition, the parametric analysis has evaluated the effect of climatic conditions (temperature and humidity) on the required distances for spray droplets to fully evaporate. The presented results could help in designing effective and energy efficient ventilated wall cavity with spray evaporative cooling systems to condition buildings in hot and dry climates. [ABSTRACT FROM AUTHOR]

This paper presents the concept of a sensible heat Electric Thermal Storage (ETS) system dedicated to household central heating. ETS is the technology of converting off-peak electricity into heat and using it in household heating 24 h a day. An ETS system is comprised of electric heating elements which are embedded within a high-density solid matrix. Since the thermal energy is stored in the solid matrix during off-peak hours and is discharged during peak hours, it results in significant savings in the household heating cost. A numerical model is developed to analyze the performance of the ETS unit, the central component of the presented system. The energy conservation equations for the solid matrix and air domains are formulated. Solid matrix is modeled as a porous medium, where radial heat conduction is neglected. The governing system of differential equations with boundary and initial conditions is solved using the Finite Volume Method. The developed model allows determining the air temperature at the outlet of the Electric Thermal Storage unit. Despite the simplified assumptions considered in the numerical model formulation, a good coincidence of the computation results with experimental data is reached. The heating system proposed in the paper meets the air quality requirements imposed by the environmental regulations and is an efficient and environmentally friendly heating systems for residential buildings. [ABSTRACT FROM AUTHOR]

Envelope systems are the main contributors to the energy consumption associated to cooling or heating buildings. There have been significant research efforts to improve the performance of building envelope systems by integrating passive cooling strategies to reduce cooling loads and maintain acceptable indoor thermal comfort. The ventilated wall cavity system is one of these passive-cooling strategies that have received considerable attention recently due to the significant benefits of reducing thermal loads of buildings. In particular, evaporative cooling inside ventilated wall cavities is an attractive passive cooling technique especially in hot and dry climates. This paper presents the initial findings of a current research study focusing on improving the ventilated wall cavity with spray evaporative cooling system that produce fine water droplets. Specifically, this paper describes a numerical modeling approach to evaluate the performance of the proposed passive cooling system to cool buildings in hot and dry climates. The simulation results suggest that a significant reduction in cooling loads can be achieved since the wall cavity can absorb heat from the indoor and outdoor while inducing acceptable supply air temperature capable of maintaining indoor thermal comfort within buildings. [ABSTRACT FROM AUTHOR]

This paper uses the numerical method and laboratory and field tests to determine the effect of cold source on groundwater source heat pump (GWHP) in Jiagedaqi. Cold sources are distributed in a scattered pattern, with temperatures ranging from 0 °C to 1 °C according to temperature field test results. Laboratory tests show that the thermal physical parameters of pebbles and grit present discrete phenomenon with depth and that the parameters of sandstone and granite undergo minimal change. By considering the correlation and discrepancy of laboratory and field tests and by modifying the parameters of the laboratory test via the analytic hierarchy process, this paper selects formation thickness, moisture content, density, and permeability as the main factors that influence the difference in thermal physical parameters. Basing on the geological conditions of the region, this paper constructs a numerical model with the data from modified laboratory tests and in-situ thermal response tests. The model analyzes heat breakthrough and influence radius of cold source in the producing/injecting system of multiple wells. Simulation results show that the influence range of cold source on GWHP is 150 m and that heat breakthrough is observed when the influence radius is less than 85 m. [ABSTRACT FROM AUTHOR]

This paper describes the process of validation of the numerical model and its calibration, based on long-term field studies that were carried out at a growing tunnel system for Agaricus bisporus in southern Poland. A verification of uncertainty indices was undertaken, based on which the applicability of the model for further research and analysis was assessed according to commonly used guidelines. WUFI®plus software was applied based on the numerical elementary balance method (EBM). The HVAC system was also simulated in order to reflect actual conditions as accurately as possible. The correctness of the model was assessed by means of uncertainty indicators in the form of the normalised mean deviation error (NMBE) and the Coefficient of Variation of the Root Mean Square Error CV (RMSE). The analysis provided an opportunity to highlight the validity of the calculations, considered reliable under the criteria adopted. It also pointed out some limitations of the model applied, resulting in negative calibration results for a small number of selected measurement monitors. Using the validated calculation model, heat flows from the ground to the building and the other way around were estimated. The specifics of the building contributed to the occurrence of heat gain from the ground being 20 times larger compared to energy losses to the ground. This opens up a potential path for extending the numerical analysis to optimise energy management for the investigated facility and to determine the thermal interaction between buildings in the surveyed area. [ABSTRACT FROM AUTHOR]

Abstract: The paper suggests a multi-criteria approach for the energy refurbishment of historical buildings, proposing methodologies for the performance analysis, coupling several experimental and numerical studies. The target consisted in a rigorous evaluation procedure, in order to guarantee the necessary reliability of a numerical model of the system “building envelope/technical plants”, on which testing the technical and economical convenience of energy retrofit solutions. The paper collects the long work carried out by several Institutions during the last years, on Building “Palazzo dell’Aquila Bosco-Lucarelli”, a historical building located in Benevento (Southern Italy), currently analyzed in order to define the technical adoption of possible improving actions. The carried out studies, beyond the proposition of an operational methodology, are aimed to evidence a best-practice specified for the Italian territorial context, which has several historical buildings needing restoration. Carefully applied investigations, based on various methodologies and through several instrumentations, allowed the definition of a numerical model correspondent to the real building, defined also comparing the results with the historical requests of gas and electricity. Moreover, dynamic energy simulations tested the effectiveness, singularly and coupled, of several solutions for the building energy optimization. A significant potentiality of energy and economic optimization has been demonstrated. [Copyright &y& Elsevier]

Abstract: In this paper, a calculation method for the floor surface temperature in radiant floor heating/cooling system is proposed, a new formula is derived to estimate the floor surface temperature. The floor is divided into two layers. The correlation for the thermal conductivity of the lower layer is developed based on the numerical model of the radiant floor system built in this paper. The results show that the floor surface temperature values from the proposed method are in agreement with the experimental and numerical values. [ABSTRACT FROM AUTHOR]

This paper reports on the improvement and application of a new method for the prediction of earth-contact heat transfer. In previous studies the new method was claimed to be fast, accurate and flexible as a result of incorporating elements of the response factor method into a finite volume technique based numerical model. Initially, a ‘pre-processing’ procedure is required to generate a certain number of hours for use as a time-series by the response factor technique in the second stage of the method. This paper shows that, it is possible to further improve the speed and accuracy of the ‘pre-processing’ procedure without losing the advantage of flexibility that the numerical models provide in the design of such cases. The improvement of the new method is presented which makes use of a ‘time-stepping control scheme’. A simple ‘extrapolation’ technique has been demonstrated previously. This method proved to be accurate and fast in solving the three-dimensional earth-contact heat transfer, which may involve a certain number of heating zones (rooms) interacting with several different temperature profiles. A multi-room configuration is utilised in this study and simulations are performed over one or more years according to the initial ground domain temperature conditions. [Copyright &y& Elsevier]

In order to meet the mid-century carbon reduction targets and to mitigate climate change and global warming it is imperative that embodied greenhouse gases (GHGs) emissions in the built environment receive immediate attention from policy, industry and academia. While academic research has grown in recent years, the uptake of embodied carbon assessments in practice has been slower. This paper reports the findings of a collaborative project between industry and academia to shed light on how to accelerate a wider uptake of embodied carbon assessments in buildings. Five projects have been each examined by three assessors (independent environmental consultants) for a total of fifteen detailed assessments. Results are presented for each of the five case studies, showing elements of agreement and, most often, of variation. Additionally, each of the life cycle stages as defined by the TC350 standards is analysed both numerically and in terms of its contribution towards the whole life embodied carbon. The results show that significant discrepancies consistently exist even when the initial information available to the assessors is the same. The numerical analysis also reveals that all life cycle stages account for important shares of the whole life carbon, and that therefore partial assessments – e.g. cradle-to-gate - are not sufficient if carbon reductions are to be realistically achieved. Future research in the field should continue to address the challenges identified in this article and work towards greater understanding and reliability of the numbers produced. [ABSTRACT FROM AUTHOR]

Operating parameters of a membrane-based parallel-plate liquid desiccant dehumidification system are investigated in this paper. The liquid desiccant and air are in a cross-flow arrangement, and separated by semi-permeable membranes to avoid carry-over problem. A numerical model is developed to simulate the system performance, and validated by experimental and analytical results. Impacts of main operating parameters on the system performance (i.e. sensible, latent and total effectiveness) are evaluated, which include dimensionless parameters (i.e. solution to air mass flow rate ratio m * and number of heat transfer units NTU ), solution properties (i.e. concentration C sol and temperature T sol ) and inlet air conditions (i.e. temperature T air,in and relative humidity RH air,in ). It is found that m * and NTU are two of the most important parameters influencing the system effectiveness. Even though the system performance can be improved by m * and NTU , its increasing gradient is limited when m * and NTU exceed 1 and 4 respectively. Decreasing solution temperature does not make a great improvement to the system performance, however, increasing solution concentration is a good approach to enhance the latent effectiveness without influencing the sensible effectiveness. The system shows the broad adaptability in various weather conditions, and has the ability to provide relative stable state supply air. [ABSTRACT FROM AUTHOR]

The importance of embodied energy and embodied greenhouse gas emissions (EEG) from buildings is gaining increased interest within building sector initiatives and on a regulatory level. In spite of recent harmonisation efforts, reported results of EEG from building case studies display large variations in numerical results due to variations in the chosen indicators, data sources and both temporal and physical boundaries. The aim of this paper is to add value to existing EEG research knowledge by systematically explaining and analysing the methodological implications of the quantitative results obtained, thus providing a framework for reinterpretation and more effective comparison. The collection of over 80 international case studies developed within the International Energy Agency’s EBC Annex 57 research programme is used as the quantitative foundation to present a comprehensive analysis of the multiple interacting methodological parameters. The analysis of methodological parameters is structured by the stepwise methodological choices made in the building EEG assessment practice. Each of six assessment process steps involves one or more methodological choices relevant to the EEG results, and the combination potentials between these many parameters signifies a multitude of ways in which the outcome of EEG studies are affected. [ABSTRACT FROM AUTHOR]

• A innovative and efficient model was proposed for multi-lane highway. • The learning was collected a lot of existed pavement segments and built a large-scale highway network. • The LCA and LCCA was integrated to assess the sustainability of the M&R decision. • GDE3 performs well in selecting more cost-effective M&R optimization. A pavement maintenance and rehabilitation decision-making model plays a significant role in the sustainable development of highway networks. However, various maintenance and rehabilitation models lack the capacity to provide multi-objective maintenance decision-making strategies, which are solely concerned with reducing maintenance costs. This study aims to propose a multi-objective maintenance decision-making model, called the Pavement Maintenance-Generalized Differential Evolution 3 (called PM-GDE3), by integrating the pavement condition indices and the generalized differential evolution 3 (GDE3) method. Economic aspect, pavement sustainability, and environmental dimensions were considered in the proposed model to increase the flexibility of pavement management. In this study, the widely-used PAVER maintenance system,which represents a conventional M&R decision-making model and the PM-GDE3 model were applied to estimate the optimal maintenance and rehabilitation schedules for the highway networks, and the results from these models were compared. The results show that the maintenance strategy obtained from the PM-GDE3 model maintains the highway in an acceptable condition. In addition, it has been found that the PM-GDE3 model saves 30.9% of maintenance expenses, about 169 million CNY, 16.9% of carbon emissions, around 4,469 kt, and 11.6% of energy consumption, 2.8GJ, for as long as 30 service years compared to the PAVER model. The PM-GDE3 model outperforms the widely used PAVER maintenance system due to its capacity to propose the optimal solution by establishing a real-time simulation with numerous pavement conditions after maintenance application. This field is the first attempt to combine pavement performance prediction model, life cycle assessment method and life cycle cost assessment. The achievements of the paper are expected to combat the impending energy crisis and climate change impacts of pavement maintenance and rehabilitation. [ABSTRACT FROM AUTHOR]

This study is focused on the evaluation of the effectiveness of vacuum insulation panel (VIP) for typical Mediterranean climate. The interest for this material is due to indisputable advantages in term of insulation performance both for new and refurbished buildings; mainly in retrofit design, adoption of lower thickness assure same results with less invasive interventions. The problem is the behavior during the summer period, not investigated in the available scientific literature. Numerical and experimental approaches are used in this paper to compare the performance of several wall packages integrating VIP with constructive technologies that result in different stationary and dynamic parameters. More in detail the results of a yearly measurement campaign in three real building of south Italy are presented; recorded data of the surface and the mean air temperatures as well as of the heat flux are commented. Data for one typical week of each season are evaluated to compare the wall made of concrete block and vacuum insulation material with a massive structure and also with a concrete wall with expanded polystyrene as insulation material. Furthermore, simulation results (by means of EnergyPlus) are presented to study, mainly during the summer, the effect of integration of vacuum insulation panel in multi-layered wall made of concrete blocks with different values of density and thermal conductivity; moreover these configurations are compared with a wall made of innovative insulated interlocking brick and with the wall types considered in the experimental phase. Using a typical office building as case study, energy consumptions and environmental and economic indexes are valuated. Experimental and numerical results show the effectiveness of solution with VIPs also for Mediterranean climate. [ABSTRACT FROM AUTHOR]

Ubiquitous modernization of building energy and management systems brings tendencies for an effective integration of renewables in buildings. This article shows how solar energy can be in charge of energy savings within a building by integration of solar systems with Trombe wall. Numerical calculations of Trombe wall thermal resistance and its performances in comparison with a common wall are considered. Additionally, energy-efficiency gaining by a combination of PV modules and Trombe wall, using simulations by SAM (System Advisor Model) software is discussed. PV module parameters and their impact on its electricity production are observed and analyzed. The PV module parameters, analyzed in the paper are: the tilt angle α of PV modules, incident angle β of direct sunrays on PV modules, normal beam irradiation N and PV cells operating temperature. With bigger incident angle β of direct sunlight on PV modules, the normal beam irradiation is smaller, which brings less electricity production. The impact of PV module operating temperature can be neglected in comparison with the impact of tilt angle on PV module electricity production. The optimal tilt angle of PV modules for generating maximum annual electricity is around latitude angle. It varies with normal beam irradiation to achieve the maximum monthly electricity production. [ABSTRACT FROM AUTHOR]

The use of task/ambient conditioning (TAC) systems can help improve thermal comfort and indoor air quality, and reduce the energy consumption in bedrooms in residences or guestrooms in hotels at nighttime for sleeping. However, its operational and energy saving performances would be affected by a number of factors, such as supply air flow rate and temperature, and supply vane angles. This paper reports on optimizing numerically the operating performances of a novel bed-based TAC system. Firstly, the methods on a novel bed-based TAC system are introduced, including the experimental method and the computational method. Secondly, the numerical model is validated using the experimental results at the experimental operating conditions. Thirdly, the operating performances of the novel bed-based TAC systems at non-experimental operating conditions using the validated numerical model are optimized and the results reported. Finally, the conclusion and limitations of the study are given. The numerical study results showed that by suitably controlling its supply air flow velocity and temperature, and supply vane angle, the bed-based TAC system can be operated to maintain an acceptable level of thermal comfort without the cold draft in an occupied zone at a low energy consumption. [ABSTRACT FROM AUTHOR]

This paper presents a numerical analysis of the desiccant air conditioning system with a cross-flow Maisotsenko cycle (M-Cycle) heat and mass exchanger (HMX). Presented mathematical models of the desiccant wheel and HMX are based on the ε-NTU method. The mathematical model of the desiccant wheel is also supplemented with algorithm allowing the accurate approximation of the initial conditions to reduce the calculation time. The novel system was compared with a conventional solution to show its application potential. The main advantage of the novel system is that it can provide comfort condition even with less effective dehumidification. Also impact of several operational factors (i.e. inlet air temperature and humidity, outdoor and regeneration airflow rate and rotational speed) on the performance of the system were investigated. The analysis of novel system were performed under assumption that the desiccant wheel is regenerated with air heated to the relatively low temperature which can be produced with solar panels in typical moderate climate conditions. [ABSTRACT FROM AUTHOR]

The total energy demand of data centres has experienced an important increase in the last years. This is why data centres industry and researchers are working on implementing energy efficiency measures in data centre portfolio. The cooling system of these unique infrastructures can account for 40% of the total energy consumption. Therefore, air management plays an important role to reduce operating costs and to increase overall cooling system efficiency. In order to improve and optimize the energy consumption and thermal management in data centres, appropriate metrics are imperative to evaluate their efficiency and performance. The present paper examines the air management of a real data centre by the use of the most promising air metrics. Noticeable air recirculation and hot spots were observed in the facility. Dynamic modelling was used to evaluate the benefit of air inefficiency mitigation. The combination of air management improvement with increasing the supply air temperature and reducing the air flow rate would allow important energy reduction in the cooling system. [ABSTRACT FROM AUTHOR]

Climate changes and urban sprawl dramatically increase the urban temperatures and the thermal quality in the built environment. Among several proposed mitigation techniques, cool roofs have now reached a broad audience, while the cool materials potentialities for façade applications are still little investigated. A novel masonry paint, produced with the inclusion of cool pigments, is investigated in this paper. A palette of colour is developed with the objective of covering a wide range of architectural integration solutions. Reflectance and emissivity are measured and calculated. The results strongly depend on the base colour used to prepare the sample; solar reflectance increase up to 0.16 is achieved for dark colours. A numerical analysis is carried out to evaluate the impact of the cool paint on the thermal response of a typical Italian residential building. Energy uses are calculated for different insulation levels and climatic conditions. Cooling energy uses are reduced in the 10–20% range; total energy uses are affected by several parameters with 5% maximum savings. Peak operative temperature reductions range from 0.5 to 1.6 °C for the building in free floating conditions, according to climate and insulation level. External surface temperatures are reduced above 6 °C during the peak irradiation hours. [ABSTRACT FROM AUTHOR]

The objective of this study is to understand the role of life cycle analysis (LCA) in building system design process based on survey inputs from building system designers and a numerical sensitivity analysis. This paper first presents findings on the perceived importance of building life cycle assessment completed by 96 practicing designers from August 2012 to April 2013. The majority of respondents, approximately 70%, work as building system designers in the U.S. The building system designers are divided into three categories: (1) enclosure system designers, (2) mechanical system designers, and (3) designers working on both systems. One of the major survey findings is that life cycle assessments are much less used in building system design than energy simulations. The primary reason for performing a life cycle analysis for a building design project is a requirement from a building owner. Furthermore, Fisher's test shows that respondents’ profession, company size, and work experience have significant correlations with the deployment of energy simulations and life cycle assessments in building design projects. ANOVA-based analyses demonstrate that there is no statically significant difference among the three categories of system designer responses on the importance of building components and design selection criteria. Interestingly, the sensitivity analyses performed for the medium size DOE (Department of Energy) reference building indicate that wall assemblies have a much larger impact on building life cycle costs than window properties. The comparison between sensitivity analysis and survey results indicates that the influence of window properties on life cycle cost is over estimated by most of the surveyed participants. Overall, this study revealed that LCA is still not widely used in the building industry even though it would help address design biases toward building systems that do not deliver the expected performance. [ABSTRACT FROM AUTHOR]

Sandstones are widely used in historic buildings. To assess energy and moisture performance of these buildings and find suitable retrofit strategies, thermal and hygric properties of sandstones are needed. Sedimentary structure of sandstones leads to their directionally dependent properties. In this paper, hygrothermal properties of four sandstones are experimentally investigated and each sandstone is characterized in the directions parallel and perpendicular to the bedding plane. Thermal properties of the studied sandstones are comparable between two directions, while moisture transport properties have a pronounced directional dependence. Lower liquid water conductivity and water vapor diffusivity occur in the perpendicular direction, which is validated by the phenomena observed from water absorption and drying tests. By conducting a benchmark case, the influence of hygrothermal property anisotropy on the thermal and moisture responses of the construction is illustrated. The results show that the property anisotropy has a weak impact on the thermal behavior, but has a strong influence on the moisture behavior, which further affects the thermal behavior due to material's moisture dependent thermal conductivity. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the typical indoor environment in Tibetan residential dwellings, which has particular architectural form and environmental adaptations. The field measurements during the summer month show that the traditional house presents high humidity, low temperature. And the indoor environment is much worse in winter. Tibetan architectural features and ethnic customs are taken into account in the creation of passive renovations that are applied with minimal effect on the overall architecture. Numerical simulations of the indoor thermal environment are conducted on the building models using DeST-h. Different renewal measures are evaluated in terms of how much they decrease annual energy consumption. Orthogonal experiments are designed to optimize an array of energy-saving building renovations to reduce energy consumption and improve indoor thermal comfort of Tibetan residential houses. Results show that there is an obvious reduction of energy consumption by combining appropriate renovations based on orthogonal optimization. The conclusion is that there are economic and environmental benefits of using natural passive methods without considering mechanical ways. The renovations are verified as effective for reducing energy consumption and improving indoor comfort in such Tibetan residential dwelling. [ABSTRACT FROM AUTHOR]

Data centers are approximately 50 times more energy-intensive than conventional office buildings, where ICT equipment consumes about 50% of total electricity and cooling energy is roughly 35% or more of total energy use. The main objective of this study is defined by energy analysis process, numerical studies, and simulation studies to assess each technical component's influence in order to create energy-optimized data centers. This includes dedicated cooling system and design conditions that were previously not generally used, how these affect energy efficiency, and how the prioritization of system selection is derived. Energy simulation programs have become more sophisticated through constant maintenance over many years. Those who have attempted to model data center design loads and annual energy consumption have found that the suite of available commercial programs for occupied office spaces is not easily adaptable to data center projects. Data centers have very simplistic load-contributing components but highly complex load growth and system growth modeling challenges. This paper addresses modeling needs that are unique to data centers, including using both hourly energy simulation programs, as well as more simplistic approaches. The developed data center energy evaluation methodology and program should be used by engineers and designers to assess the effectiveness and economic benefits of cooling systems. [ABSTRACT FROM AUTHOR]

Natural ventilation is a promising approach to reducing building energy use if designed properly. Most of the previous design models for calculating airflow due to single-sided natural ventilation have been based on the assumption of simple openings. Since, most windows are not simple openings, but rather can create flow obstructions when opened; the impact of window structure on ventilation needs to be accounted for in order to accurately predict the ventilation rate in buildings. This paper presents an experimental and numerical evaluation of the impact of three types of windows—hopper, awning, and casement—on airflow in the case of single-sided natural ventilation. Semiempirical models for predicting the ventilation rate were developed for these window types and validated by both large-eddy simulations and full-scale measurements. In general, the predictions agreed with the measured results within an error of 25%, and the new models can be used for the design of natural ventilation systems. [ABSTRACT FROM AUTHOR]

The building envelopes are exposed to the hot-humid climate with high humidity in hot summer and cold winter zone (HSCW) of China. The moisture transfer may severely influence the conduction loads through exterior walls. In this paper, a coupled heat and moisture transfer model is developed and validated to investigate the thermal performance of exterior walls. The conduction loads through a typical exterior wall are used to evaluate the effect of moisture transfer on the thermal performance of exterior walls in HSCW zone of China. The results show that the peak cooling and heating loads are overestimated by 2.1–3.9% and 4.2–10.1%, respectively, when ignoring moisture transfer. In cooling season, the sum of the latent load accounts for 14.3–52.2% of the sum of the total load and the yearly latent load accounts for 4.9–6.1% of the yearly total load when considering moisture transfer. The total cooling, heating and the yearly load are underestimated by 9.9–34.4%, 1.7–4.0%, and 5.2–6.8%, respectively, when ignoring moisture transfer. The results indicate that ignoring moisture transfer causes significant discrepancy in predicting the conduction loads. A detailed model considering moisture transfer in building envelope is essential to accurately evaluate the building energy performance in HSCW zone of China. [ABSTRACT FROM AUTHOR]

This paper reports a numerical investigation of the buoyancy induced turbulent air flow in an inclined passive wall solar chimney (IPWSC) attached to a room (ventilated space) for ventilation applications over a range of controlling parameters. The standard k − ɛ turbulence model has been employed to model air turbulence in the solar chimney system. With an isoflux heating condition specified on the absorber wall, the ventilation performance of the IPWSC design has been examined over the Rayleigh number range of 1.36 × 10 13 ≤ Ra ≤ 1.36 × 10 16 and inclination angles from 0̊ to 6̊. The present numerical result shows that the turbulent kinetic energy and turbulent intensity in the solar chimney decrease with the increase of the inclination of the passive wall. The effectiveness of the IPWSC design for enhancing the thermally driven ventilation has been confirmed. Additional simulations have been carried out with a standalone solar chimney model. The result shows that the standalone model over-predicts the mass flow rate compared to that predicted by the attached model. The average difference in the predicted mass flow rates between the standalone model and the attached model with inclination angles from 0̊ to 6̊ at a representative Rayleigh number of Ra = 1.36 × 10 14 is around 10%. [ABSTRACT FROM AUTHOR]

Appropriate design and control strategies are crucial for the implementation of certain complex active systems in the building sector. Suitable and user-friendly numerical tools have to be available to architects and engineers, so they can incorporate innovative active systems in their building designs. The thermal response of a ventilated facade with phase change material in its air chamber for cooling applications is studied in this paper. The system makes use of low temperatures at night to solidify the phase change material, and store it solid for a later cooling supply to the interior of the building. This active technology is very sensitive to the weather conditions as well as to the defined operational schedule (charge, storage and discharge periods definition). Two different numerical approaches have been developed to better understand this system and to define different control strategies, as well as to determine their potential to reduce the energy consumption in the building for cooling purposes. First, a finite control volume approach was applied to describe the ventilated facade with latent heat storage. The important computational cost and complexity of this numerical methodology leaded the authors to develop a simple numerical model based on the assumption that the exchange between the air and phase change material inside the ventilated facade occurs at isothermal conditions. Both models were validated against experimental data, and even though the isothermal model presented slightly higher deviation from the experimental results than the finite control volume one, it is presented as a suitable numerical tool for architects and engineers because of its light computational cost and versatility. [ABSTRACT FROM AUTHOR]

In this paper, an experimental and numerical approach to the characterization of thermal bridges is presented. The need for this characterization was found within an experimental study in a 2 floor high façade. This façade was constructed with 3 concrete elements which were placed in it to produce a similar thermal bridge effect to the one created by floor slabs traditional building construction in Spain. Commonly applied thermal assessments perform one-dimensional heat transfer analysis over planar elements such as the façades studied in this experiment. However, it is well known that thermal bridges are locations in buildings where one-dimensional heat transfer analysis cannot be applied. This problem was approached by creating a numerical 2D thermal model which was calibrated against experimental data from several temperature and heat flux sensors which were located at specific points in the thermal bridge elements. [ABSTRACT FROM AUTHOR]

This paper provides a comparative study of the energy efficiency of a conventional ventilating and air conditioning (VAC) system with three configurations. This system was used to cool an experimental room in an office building in more control scenarios realised by adopting different cooled water temperatures and chiller cooling systems. In this purpose, an air–water mist cooled system for an air-cooled chiller is proposed. Depending on the components, the analysed VAC system has the following configurations: (1) air handling unit (AHU) and fan-coil units (FCUs); (2) air handling unit (AHU); and (3) heat recovery unit (HRU) and fan-coil units (FCUs). The electricity consumption weight of the equipment of each VAC system, the total energy consumption and the influence of control parameters on this consumption are analysed. The results of the experiments indicate that the optimal efficiency VAC system in office buildings includes an AHU and FCUs with an air–water mist cooled chiller and a cooled water temperature of 8 °C. For this system, a mathematical model is developed to minimise the electricity consumption by optimal control, where the consumption depends only on non-controlled parameters (solar radiation intensity and outdoor air temperature). This model is verified with actual measurements to confirm its accuracy, and a good agreement between the prediction and measurement is achieved. Additionally, the assessment of thermal comfort in the experimental office is performed based on the PMV-PPD model using the ASHRAE Thermal Comfort programme. The obtained results demonstrate that the AHU&FCUs system assures an increase in thermal comfort. Finally, a TRNSYS simulation model of energy consumption and PMV-PPD indices for the AHU&FCUs system is developed and experimentally validated. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of the coupled heat transfers in hollow tile with two air cells deep in the vertical direction and three identical cavities in the horizontal one, uniformly heated from below or from above. The end vertical side walls of the structure are assumed to be adiabatic. The Boussinesq approximation is invoked and the flows are considered laminar and two-dimensional for the whole range of parameters considered. Conduction heat transfer in the solid partitions and radiation exchange between gray and diffuse surfaces are accounted for. The governing equations are solved by finite difference technique based on the control volume approach and the SIMPLE algorithm. Based on steady state simulation, the appropriate overall thermal conductances U ′ are derived for the two considered situations (heating from below and from above). The results show that the hollow block with two air cells deep in vertical direction permits a considerable reduction of heat transfer between the inside and the outside of the building roofs. [ABSTRACT FROM AUTHOR]

The aim of this paper is to provide a numerical simulation for giving a technical answer to some problems that a structural engineer has to solve when designing a timber building based of Platform Frame technology, i.e., composed of light-frame timber shear walls. For a fully anchored wall, a finite element model, aimed at determining wall stiffness, strength and ductility, is presented. The shear wall is considered as lacking of any constructive imperfection. [ABSTRACT FROM AUTHOR]

The thermal behaviors of a solar chimney incorporating with organic phase change material (PCM) RT-42 unit under different heat fluxes are studied in this paper. For the numerical model, effective heat capacity method is employed to analyze the performance of RT-42, while the average thermo-physical property approach is used to describe the PCM/fins component. The PCM behaviors during its melting and solidification processes, absorber surface temperature, mass flow rate, and inlet and outlet air temperature difference have been investigated. The numerical results give good agreements with the experimental results. The comprehensive investigations under various heat fluxes from 100 to 800 W/m 2 are carried out by using the verified model. The numerical results show that the performance of the system deteriorates sharply once the heat flux is or lower than 500 W/m 2 , but not big improvement if the heat flux is higher than 700 W/m 2 . Therefore, the performance of the system is highly dependent on the solar radiation. The application of high effective thermal conductivity enhancers can further improve the performance of the chimney under lower solar radiation. [ABSTRACT FROM AUTHOR]

One potential solution for stand-alone power generation is to use hybrid energy systems with hydrogen storage. In this paper, the physical behaviour of a hydrogen energy system with renewables has been numerically simulated and experimentally re-enacted. A reference household in Slovenia's coastal region was used to identify the optimal energy system design, by considering the geographical location, availability of energy sources, actual load dynamics, and components’ technical and economical characteristics. The results show that optimal electricity supply is technically feasible with a 100% renewable system, consisting of wind turbines and solar photovoltaic arrays, including hydrogen technologies (electrolyser, hydrogen tank, fuel cell). The optimal feasible system capacity (33 kW), with the lowest total net present cost (€136,063), is approximately eight times larger than the peak power demand (3.8 kW). The experimental work was performed at hydrogen laboratory facilities. Experiments proved the possibility of alternative uses of existing industrial hydrogen technology for balancing power supply and demand, with a mere 3% deviation from numerical results [ABSTRACT FROM AUTHOR]

Abstract: This paper reports on the thermal and optical characterisation of PCM (phase change material) RT27 using the T-history method and spectrophotometry principles, respectively, and the experimental and numerical performance evaluation of a PCM-glazed unit. Various relationships describing the variations in the extinction, scattering and absorption coefficients within the phase change region were developed, and were validated in a numerical CFD model. The results show that: (i) during rapid phase changes, the transmittance spectra from the PCM are unstable, while under stable conditions visible transmittance values of 90% and 40% are obtained for the liquid and phases, respectively; (ii) the radiation scattering effects are dominant in the solid phase of the PCM, while radiation absorption dominates in the liquid phase; (iii) the optical/radiation performance of PCM can be successfully modelled using the liquid fraction term as the main variable; (iv) the addition of PCM improves the thermal mass of the unit during phase change, but risks of overheating may be a significant factor after the PCM has melted; (v) although the day-lighting aspects of PCM-glazed units are favourable, the change in appearance as the PCM changes phase may be a limiting factor in PCM-glazed units. [Copyright &y& Elsevier]

Abstract: The technology of embedding heat exchange tubes in diaphragm walls is a new direction for Ground-coupled Heat Pumps (GCHP). This paper examines the heat transfer model and design method for geothermal heat exchangers in diaphragm walls, which are seldom investigated in the world. Two-dimensional (2D) heat transfer models for diaphragm wall heat exchangers (DWHE) are established. A design method for DWHE is further developed to calculate the hourly heat exchange capacity of DWHE and to get the reasonable design parameter of DWHE. The DWHE model over the excavation line has the same changing trend with numerical solutions, and the relative errors between them are less than 2%. The relative errors of calculated heat exchange rate per meter using DWHE model and measured data are less than 6% after running 10h. The relative errors of temperature between DWHE model under the excavation line and the measured data at different positions are no more than 9%, whereas the relative error between the tradition models in GCHP (line source model and finite-line source model) and the measured data may reach as much as 40%. [Copyright &y& Elsevier]

Abstract: This paper presents a method for optimal sizing of a standalone PV system for remote areas in Sohar, Oman. PV array tilt angle as well as the size of the system's energy sources are designed optimally for better performance and lower energy cost. Numerical methods for optimization of the PV module tilt angle, PV array size and storage battery capacity are implemented using MATLAB and hourly meteorological data and load demand. The results show that for Sohar zone the tilt angle of a PV array must be adjusted twice a year. The PV array must be slanted at 49° in the period of 21/09–21/03 (n =255–81), while it must be horizontal (tilt angle is zero) in the period of 21/03–21/09 (n =81–255). This adjustment practice gains the energy collected by a PV array by 20.6%. As for the PV system size, the results show that the sizing ration of the PV array for Oman is 1.33 while the sizing ratio for battery is 1.6. However the cost of the energy generated by the proposed system is 0.196USD/kWh. [Copyright &y& Elsevier]

Abstract: This paper aims to explore how and where phase change materials (PCMs) are used in passive latent heat thermal energy storage (LHTES) systems, and to present an overview of how these construction solutions are related to building''s energy performance. A survey on research trends are firstly presented followed by the discussion of some physical and theoretical considerations about the building and the potential of integrating PCMs in construction elements. The different types of PCMs and main criteria that govern their selection are reviewed, as well as the main methods to measure PCMs’ thermal properties, and the techniques to incorporate PCMs into building elements. The numerical modeling of heat transfer with phase-change and heat transfer enhanced techniques are discussed, followed by a review of several passive LHTES systems with PCMs. Studies on dynamic simulation of energy in buildings (DSEB) incorporating PCMs are reviewed, mainly those supported by EnergyPlus, ESP-r and TRNSYS software tools. Lifecycle assessments, both environmental and economic are discussed. This review shows that passive construction solutions with PCMs provide the potential for reducing energy consumption for heating and cooling due to the load reduction/shifting, and for increasing indoor thermal comfort due to the reduced indoor temperature fluctuations. [Copyright &y& Elsevier]

Abstract: Heat flow through the roof contributes in the total heat gain of a building. The contribution becomes more severe for single story houses covered by metal sheet roofing. This paper presents a new design for metal sheet roofing structure in order to improve its total thermal resistance. Its main concept is to utilize phase change material properties to firstly absorb the downward heat flow made by incident solar radiation to the room and then release it back to the environment by means of the naturally favored external convection especially during the nocturnal cycle. Experimental and numerical analyses have been conducted to compare thermal performance of the new design and the available normal roofing with the same materials and color. A general mathematic equation system, which can be used for further evaluation and prediction of the new design with varied parameters, has been derived for the thermal process through the roof. The results show that the new design can effectively reduce the downward thermal flow through the roof into the house. As a consequence, the cooling load of the house can be lower and more electricity for cooling attempt can be saved. [Copyright &y& Elsevier]

Abstract: This paper investigates design features that can potentially reduce the energy consumed in attaining appropriate thermal comfort levels in typical residential buildings. A numerical model coupled with a PID controller is developed to predict the indoor air temperature that is adjusted via mechanical ventilation. The model is used to simulate and evaluate various scenarios of building wall layouts and materials. From the various simulation runs, the wall configurations and materials were refined to combinations that rendered the mechanical ventilation a feasible option for attainment of comfort for the largest number of hours per year. The runs were conducted for a typical residential apartment located in the city of Beirut, Lebanon, which is characterized by mild coastal climatic conditions. Different wall configurations were assumed for each of the living zone and the bedroom zone of the apartment. The simulation results suggest an optimal wall configuration comprised of a 5cm layer of insulating strawboard sandwiched between a 2cm×10cm wall made of masonry units consisting of Hempcrete (mixture of Portland cement, aggregates, and industrial hemp fibers) for the living zone, whereas the wall for the bedroom zone consists of a 10cm of Hempcrete. [Copyright &y& Elsevier]

Abstract: Complaints on thermal comfort and confusions on cooling load calculation are still two main issues for the design of stratified air distribution (STRAD) system. This paper investigated these two issues for STRAD systems applied in a large space lecture theatre. The simulation results revealed that best satisfied thermal environment was obtained when supplied air from floor level, terrace and desk-edge mounted grilles simultaneously. A new method for the calculation of the occupied zone cooling load, which is based on CFD (computational fluid dynamics) simulation was proposed and tried. The effective cooling load factor concept was further clarified, which can be conveniently used to calculate the occupied zone cooling load and then determine the supply airflow rate. The concepts of occupied zone cooling load reduction and the associated but different cooling coil load reduction were differentiated, and it was illustrated that cooling coil load reduction up to 16.5% of the space cooling load can be achieved with split location of return and exhaust grilles. These simulation works provide a good basis for full-scale experimental validation of the key energy saving features of a well-designed stratified air distribution system. [Copyright &y& Elsevier]

Abstract: In-home displays (IHDs) have the potential to change the way energy use feedback is communicated to householders and to induce behavioural change by providing real-time information on energy consumption. How feedback is presented to users and how users understand the meaning of such feedback depends on the design of the display interface. This paper presents a laboratory study to investigate how the user interface of energy displays might be best designed. The work studied people''s ability to spot changes in smart meters by comparing three different types of display design to see which was most effective in attracting attention to changing information, and whether the use of colour would also facilitate detecting changes. A computerised spot-the-difference task was undertaken; accuracy rates and response times were the key dependent variables, and qualitative information on participant preferences was gathered in interviews after the computerised task. Results showed that there was a difference between design types presenting the same information: simple numerical displays were superior to pictographic or analogue scale designs in both response time and accuracy. They also showed that the use of colour did not significantly affect performance. In general, participants also subjectively preferred numerical design for their in-home energy displays. [Copyright &y& Elsevier]

Abstract: Cool roofs are an emerging technique with a recent growing interest worldwide. The aim of the present paper is to present the application of cool roofs’ technology in a laboratory building located in Iraklion, Crete, Greece. The building is monitored towards its energy performance and indoor environment before and after the implementation of the cool roof technology. The specific case study is intended as a shining example of the cool roof capabilities in improving the thermal conditions in non-air conditioned and in reducing the energy consumption in air conditioned buildings. [Copyright &y& Elsevier]

Abstract: This paper describes an effort to estimate the impact of a cool roof (characterised by increased solar reflectance compared to the initial roof and high infrared emittance) on the energy performance and thermal behaviour of a non-cooled school building in Athens, Greece. An experimental monitoring campaign has been carried out before and after the application of a white elastomeric coating with a solar reflectance of 0.89 on the roof of the building. The air and surface temperature of the building have been measured and a set of meteorological parameters have been collected. An infrared camera has been used to depict the differences in the surface temperature before and after the cool roof application. The monitoring results are complemented and supported by building simulation. The building has been modelled into TRNSYS software and the model has been calibrated and validated using the experimental data. Simulation results show a decrease in the air temperature in the classes that reaches 2.8°C and a decrease in the annual cooling load by 40%. The corresponding heating penalty (i.e. the increase of heating load) is 10%. Additionally, the impact of the cool roof on thermal comfort, peak power and surface temperature has been assessed. [Copyright &y& Elsevier]

Abstract: This paper investigates wind pressure characteristics on a corridor double-skin facade (DSF) of a tall rectangular building through experimental and numerical modeling. Firstly, wind-tunnel experiments have been carried out to study the wind pressures acting on three surfaces of the corridor DSF of the building: the outside and inside surfaces of the external skin and the outside surface of the internal skin. The characteristics of the wind pressure distribution on the DSF are investigated for different DSF layouts, air corridor width and incident wind angles. The mean and standard deviation of the pressure coefficients are presented for twelve wind angles over 360°. The experimental data show complex wind pressure distributions inside and outside the air cavity. Then, the zonal approach is applied to model the inner-gap pressures on the DSF. The results from the zonal modeling compare relatively well with the wind-tunnel measurements. Thus, the zonal approach is an effective tool for evaluating the performance of DSF on tall buildings and may be an efficient alternative to the traditional wind-tunnel test and computational fluid dynamic (CFD) method. [Copyright &y& Elsevier]

Abstract: The adoption of Phase Change Materials (PCMs) in building components is an up-to-date topic and a relevant number of research activities on this issue is currently on the way. A particular application of PCMs in the building envelope focuses on the integration of such a kind of material into transparent envelope components. A numerical model that describes the thermo-physical behaviour of a PCM layer in combination with other transparent materials (i.e. glass panes) is developed to perform numerical analyses on various PCM glazing systems configurations. The paper illustrates the structure of the model, the main equations implemented and the hypotheses adopted for the model development. The comparison between numerical simulations and experimental data of a simple PCM glazing configuration is also presented to show the potentials and the limitations of the numerical model. While a good agreement between simulations and experimental data can be shown for the surface temperature of the glazing, the comparison between simulated and measured transmitted irradiances and heat fluxes does not always reach the desired accuracy. However, the numerical tool seems to predict well the thermo-physical behaviour of the system and may therefore represent a good starting point for simulations on different configurations of PCM glazing systems. [Copyright &y& Elsevier]

Abstract: This paper presents an experimental and numerical case study of the heat transfer around the helical ground heat exchanger. With varying helical pitch, indoor thermal response tests were conducted in a dry sand. The tests were analyzed based on axisymmetric finite element analyses and recently published heat source models for spiral coil heat exchanger including our modifications of them by adding finite-length line source solution to consider vertical return pipe at center of helical heat exchanger. In addition to reasonable agreements in soil temperature rises at exteriors the helical heat exchanger, existence of return pipe was found to be important for estimation of heat transfer inside helical exchanger. Besides, the heat source models were found to be applicable to approximate mean fluid temperature during TRTs. The numerical and analytical models were applied to field thermal response test for an energy pile reported in literature. Compared with numerically estimations, the analytical solutions considerably overestimated temperature rise at the exterior of the energy pile. The results reveal that reasonable considerations in estimation of effective thermal properties may be needed when applying the heat source models for energy pile, even though they would evaluate reliable heat transfer behavior of helical heat exchanger embedded in a homogeneous ground. [Copyright &y& Elsevier]

Abstract: The water-intake temperature is a key factor affecting the system energy efficiency of an open-loop surface water source heat pump system (SWHPS). In addition to the conventional single-pipe water-intake design, we proposed two new design options that can improve SWHP efficiency. The numerical model that pertains to a SWHPS is presented and parameters such as the fluid-intake temperature and energy-saving rate of the heat pump system are analyzed and compared with experimental measurements. Our results demonstrate that on the basis of energy-saving rate, reducing the velocity of the water delivery has no significant influence while intake via multiple ports delivers superior efficiency. In conclusion, the water-intake design impacts on the SWHPS energy-saving rate because of its efficiency in drawing lower temperature water from a water retention body during summer. The method presented in this paper can provide a reference for a more detailed improvement on the energy performance of an open-loop SWHPS. [Copyright &y& Elsevier]