Design Of HVAC Systems Research Articles

Powerhouse Telemark: A plus energy building with a low exergy heating and cooling system

Powerhouse Telemark (PHT) is an eleven stories high office building in Telemark in Norway, built to plus energy standard. A plus energy building that is built according to the Powerhouse definition prior to 2019 must produce more renewable, locally produced energy during the lifetime of the building, and must produce enough renewable energy to cover the total embodied energy used for the production and transportation of the building materials used in the building. The local renewable energy production must also cover the yearly net energy needs for operations, renovations and demolition of the building. The local production of renewable energy on the building is not required to cover the energy needed for plug loads in the building.The building will have a unique diamond shape, and the roof of the building is oriented towards the south, and slopes at an angle of 24 degrees from the horizontal. The building will be a net supplier of electricity when seen over a whole year.In addition to other “normal” measures to achieve a plus energy building, like a high performance building envelope, and an extremely efficient ventilation system, energy efficient lighting and equipment and a solar PV system, a new low exergy heating and cooling system has been implemented in the building. This low exergy system (called Lowex) is based on low temperature heating and high temperature cooling, which together with an optimized energy well design will give extremely low demand for delivered energy (electricity). To design this Lowex system, a lot of different calculations and simulations had to be done, both with commercial software packages, but also with new develop dynamic simulation models. These design procedures and models are described in this paper. This paper also describes how these results will be used for the operation of the building.The building is currently under construction and will be commissioned in late 2019/early 2020. The main experience from the design phase and early construction phase is that the Lowex system sets strict demands on both façade design and the interior design. Transparent vs. opaque area ratios, solar shading and glazing solutions set boundaries for the architectural concept, and must be taken into account early in the design process. Flooring materials, ratio of landscape vs. office cells, and thermal zoning of the building affects the interior design. The acoustic concept and the carbon footprint of the building as well as the design of the supplementary HVAC-system are also important factors that need to be taken into account at an early stage in the design phase. To solve these interdisciplinary problems it requires a design team that can work together closely. The architect, and the engineer that is responsible for the energy performance of the building, have a central role to play at the very beginning of the design phase when the geometry and the general parameters of the building is still in flux.

A Study on Thermal Characteristics Affected by Air Distribution System Installed in Indoor Ice Rink Arena

The Republic of Korea held the Winter Olympics in February 2018 and built several indoor ice rinks. Recently, the population of viewing and enjoying winter sports in indoor ice rink arenas is increasing and it is expected that the demand for building new indoor ice rink arenas will increase in the future. These indoor ice rinks generally should have an adequate dehumidification and heating system to provide optimal indoor air condition for users (spectators and athletes) under the required heat and humidity conditions. In addition, HVAC system designers should take steps to prevent fogging from condensation on the ice surface and to prevent condensation on the walls. This study was carried out to evaluate the formation of fog near the ice surface by using two air distribution systems applicable to the indoor ice rink arena. It was confirmed that the mixed ventilation method did not cause fog near ice surface, and that there is a great difference in the composition of the indoor thermal environment of the ice rink arena according to the type of ventilation system.

IFC based semi-automated design tool for HVAC central system: A general framework

Traditional HVAC design process contains a large amount of time-consuming work such as load calculation for each space, hydraulic calculation to determine duct size and careful duct layout arrangement to avoid collision. Computer is more suitable for such kind of “dumb” work with higher efficiency and less fault. Also present building design work is a less integrated process where engineers of each domain focus on their own work. This often result in unconformity and poor quality with limited project time. IFC is a neutral platform, open file format specification to facilitate interoperability in the architecture, engineering and construction. In this paper, we propose a general framework of an IFC based integrated semi-automated design tool for central HVAC system design. It contains four main modules corresponding to specific design procedures. Human is allowed to make decision during the design process for more flexibility.

Analysis of transient thermal sensation for “overheating” and “subcooling” conditions in a room

Thermal comfort is a very important issue for the design of HVAC systems. The aspects of thermal comfort are also significant in the operation of the heating/cooling systems in rooms. Many investigations studied the stationary boundary conditions, while transient conditions were not in focus. Therefore, this paper describes measurements carried out in a climate room under transient conditions. After an introduction, the second part of this paper gives an overview about the experimental setup and the methodology of the dynamic investigations. The third part describes the main results of the analyzes. The fourth part includes a discussion of these results and the contribution to potential regulation systems and further investigations. As a result of these analysis, it can be stated, that the individual comfort temperature as set by the user is mostly (operative room temperature). With regard to the dynamic behavior, it must be concluded that most subjects accept a room temperature increase of without directly expressing a change request. When the operative temperature falls below the individual comfort temperature, the desire for an increase in the operative temperature is immediately expressed, even in the case of small deviations. The paper ends with a summary of the results.

Design and Implementation of IoT-based HVAC and Lighting System for Energy Saving

Building Energy Management System(BEMS) technology is under study as one of the various solutions to environmental problems such as depletion of energy resources, global warming, and climate change. Solving the energy problems of the future BEMS is not the only goal. Occupants must be guaranteed a comfortable environment. HVAC systems and lighting systems are a large part of building energy consumption, which also means that it is an important part of energy conservation. In this paper, we propose IoT-based HVAC and Lighting(I-HVAC&L) system for HVAC system and lighting system management. With I-HVAC&L System, you can save energy efficiency without compromising the convenience of residents’.

Effects of the room temperature sensor position and radiator sizing on indoor thermal comfort and energy performances

In this paper, a simplified zonal model for the evaluation of the spatial distribution of the air temperature in a thermal zone is presented. This model, in which the air flow is caused only by buoyancy forces, is implemented in ALMABuild. The model is used for the analysis of the effect of the temperature sensor positioning on the control system behaviour and on the indoor comfort conditions. This analysis is performed considering a multi-zone building composed by three offices, focusing the evaluation to the central one. The office is heated by means of a radiator in which the hot water flow rate is varied by a valve controlled via a room temperature sensor. By means of numerical simulations, indoor comfort conditions, energy consumptions and control system response are evaluated for three different sensor positions (far from the radiator, in the middle of the office, close to the radiator), two radiator sizes (one obtained by imposing a high supply water temperature, 80 °C, the other a low supply temperature, 60 °C) and two control strategies (weather compensation and fast restart). The results presented in this study and demonstrate how complete dynamic energy simulation tools can provide to the designer important information, like the room temperature sensor position that should be close to the emitter and far from cold external walls, for the optimal design of HVAC systems.

環境配慮型市庁舎における空調・換気計画と温熱環境の検証 （第2報）吹抜を介した自然換気システムの計画と運用時の温熱環境・換気量の検証

環境配慮型市庁舎における空調・換気計画と温熱環境の検証 （第2報）吹抜を介した自然換気システムの計画と運用時の温熱環境・換気量の検証

Comparison of ASHRAE peak cooling load calculation methods

The building peak cooling load calculation is one of the fundamental steps to develop a proper whole-building HVAC system design. The accuracy of the calculation not only impacts the system size but also influences the building’s performance over the long run since oversized or undersized HVAC systems can exhibit less than optimal operation. Therefore, an accurate, easy-to-use method has been a goal for more than 60 years in the United States. To date, ASHRAE has published five methods for determining building peak cooling loads, including the total equivalent temperature difference/time averaging (TETD/TA) method, the transfer function method (TFM), the cooling load temperature difference/solar cooling load/cooling load factor (CLTD/SCL/CLF) method, the heat balance method (HBM), and the radiant time series method (RTSM). This article presents the results of a comprehensive comparison of these building peak cooling load calculation methods with a focus on the sensible building envelope cooling loads. The results show that the HBM is the most accurate method, followed by the RTSM, the TFM, the TETD/TA method, and the CLTD/SCL/CLF method.

Experimental investigation of a novel PVt/heat pump system for energy-efficient poultry houses

Despite the promise of abundant renewable energy resources in the world, the poultry sector is still dominated by traditional energy sources. In this study, results of a field trial of an innovative and cost-effective HVAC system design applied to a poultry house have been presented. This system comprises of two integrated novel components; a polyethylene heat exchanger (PHE) based a photovoltaic thermal (PVt) array and an efficient and innovative ground pipe array coupled to a heat pump driven HVAC system. The analysis included the daily PV electrical output and heat pump performance. The results of the experimental study reveal that 3733 kWh and 2432 kWh heat energy have been supplied in the 7-week growth cycle of chickens condition, respectively. The COP of the HP has been calculated for the winter period and observed between 2.3 and 2.43. The PV system was able to generate 1876 kWh electrical energy with potential to meet HP’s energy needs in the most energy needing period.

Investigation of maximum cooling loss in a piping network using Bayesian Markov Chain Monte Carlo method

Cooling loss during transmission from cooling sources (chillers) to cooling end-users (conditioned zones) is prevalent in HVAC systems. At the HVAC design stage, incomplete understanding of the cooling loss may lead to improper sizing of HVAC systems, which in turn may result in additional energy consumption and economic cost (if oversized) or lead to inadequate thermal comfort (if under-sized). For HVAC system sizing or retrofit, there is a lack of study of uncertainties associated with the maximum cooling loss of HVAC systems although uncertainties in predicting building maximum cooling load have been studied by many researchers. This paper, therefore, proposes a study to investigate the uncertainties associated with the major parameters in predicting the maximum cooling loss in HVAC piping networks using the Bayesian Markov Chain Monte Carlo method. Prior information of those uncertainties combined with available in-situ data, is implemented to produce more informative posterior descriptions of the uncertainties. To facilitate the application, uncertain parameters are categorized into specific and generic types. The posterior information gathered for the specific parameters can be used in retrofit analysis, whereas that acquired for the generic parameters can be referred to in new HVAC system design. Details of the proposed methodology are illustrated by applying it to a real HVAC system.

Multi-objective design optimization of a rail HVAC CO2 cycle

In HVAC system design for passenger rail vehicles minimization of objectives on merchantability (initial costs), integration (equipment mass, volume), and operation (electric power demand, noise emissions) becomes increasingly important. Identification of appropriate process and component design parameters is a significant engineering challenge, particularly for emerging R744 (CO2) refrigerant cycles.In this work the sizes of the compressor, evaporator, gas cooler, cooler fan, and internal heat exchanger, plus the high pressure level and the cooler air flow rate of an R744 cycle were subject to multi-objective genetic optimization. Computationally inexpensive artificial neural networks were used as interface between different computation tools. As a result a set of Pareto-optimal R744 cycles was obtained to support the design engineer. For minimum volume and mass (153 l, 169 kg), total electric power demand was 9.2 kW. Vice-versa, minimum power demand (6.9 kW) yielded a large (272 l), heavy (198 kg), and expensive system.

Effectiveness of a symmetric desiccant wheel operating in balanced flow condition: Modeling and application

Interest in desiccant evaporative cooling technologies is significantly increasing, thanks to the potential of realizing high energy efficiency systems and integrating renewable energy sources. The design of such HVAC systems is, however, not simple mainly due to the complex heat and mass transfer phenomena occurring in the desiccant wheel. For this reason, research effort is being focussed on the development of a simple and accurate model to predict the performance of desiccant wheels. In this work an effectiveness model is developed for the symmetric desiccant wheels operating in balanced flow conditions. Firstly, the effectiveness model is validated via comparison with a numerical model and secondly, its application is demonstrated in the experimental analysis of two different desiccant wheels. It is found that the model predicts well regardless of the differences in the technical specifications of the wheels. The model is considered appropriate for implementation in quick simulation and control programs thanks to its fast non-iterative characteristics.

基于CFD仿真和当量温度的某动车司机室气候舒适性评价研究

动车司机室内微气候热舒适性是设计初期需要考虑的重要内容，在设计前期就需要预测采暖、通风和空调(HVAC)系统对司机气候舒适性的影响。利用仿真进行前期分析具有成本低、方案修改方便、能分析出许多实验得不到的参数的优点。本文建立了某动车司机室有限元模型，利用CFD数值仿真的方法对冬季和夏季两种工况下司机室内的空气速度场和温度场进行了仿真。由于行内标准UIC651只规定了头部和小腿下方气温和气流速度的范围，对于人体详细部位的热舒适性评价无能为力，本文综合UIC标准和采用当量温度计算的方法对该动车司机室微气候进行了分析，并尝试利用Nilsson舒适度模型结合当量温度对人体舒适度进行了分析评价。结果表明，该司机室的设计能够满足司机的气候舒适性要求；此外，Nilsson舒适模型对室内热舒适性头部和小腿下方的要求与UIC651标准是一致的，但能够评价更多身体部位的热舒适性。本文的数值模拟计算和气候舒适性评价方法结果可为轨道车辆司机室布置和HVAC系统的设计分析提供参考。 The indoor microclimate comfort of EMU train driver compartment is an important concern in the early stage of design, and the influence of the HVAC system on climate comfort should be predicted. By using simulative analyses early in design, it is relatively convenient to modify the design with lower cost, and can acquire many parameters which can't be acquired by tests. In this paper, the finite element model of an EMU train driver compartment was established, and the distribution of the indoor temperature and air-flow speed were simulated for both summer and winter conditions. Since only the comfort ranges of temperature and air-flow speed near the head and below calf regions were prescribed in the UIC651 standard, which was unable to be used to evaluate the climate comfort of detailed body parts of human body. For this reason, the equivalent temperatures of human body parts were calculated, and were used to evaluate the climate comfort of driver human body by comparing with the Nilsson comfort model. The above analyses showed that the layout and the HVAC design of the EMU train compartment met the requirement of climate comfort of driver. The results also showed good consistency of Nilsson model with the UIC651 standard in evaluating head and body parts below calf, while the model could be adopted to evaluate more parts of human body. The simulative calculation and the evaluation methods of the climate comfort presented in this paper provide good references for the design and analysis of driver compartment layout and the design of HVAC system.

The spatial evaluation of the radiative human body heat exchanges: An effective contribution for limiting energy consumption and achieving better indoor conditions in buildings

Radiative heat exchanges inside buildings remarkably affect the thermal balance of the human body in confined spaces and the related thermal comfort sensations of people. The mean radiant temperature is an important component of this balance. Unfortunately, it is usually computed by means of too simplified relationships, which significantly influence the comfort evaluations. Such simplified approaches are also accountable for a less effective design of HVAC systems which, in turn, could result in high energy consumption in the climatization of buildings. However, an accurate evaluation of the mean radiant temperature, especially when high intensity sources are present in a given internal space, depends on the angle factors between human subjects and surrounding surfaces of the enclosure. Angle factors, in turn, are direct functions of the projected area factors of the human body. Presently, there is still a certain lack in the availability of simple and reliable methods for computing angle factors of people in assigned postures, particularly in case of complex geometry and presence of heat high intensity sources, like sun.A comprehensive method is here introduced for evaluating the thermal comfort conditions of indoor spaces, avoiding the difficult singling out of several algorithms, dispersed in an inorganic way in the literature. A further contribution consists in the possibility of evaluating geometrically complex enclosures also in presence of direct solar radiation entering the room. Moreover, an analytical method for computing the projected area factors, based on experimental results, obtained by means of a photographic apparatus on purpose designed, is included in the methodology.An application of the method to a typical building situation in presence of direct solar radiation is also proposed.

An Energy Efficiency Assessment of the Thermal Comfort in an Office building

People spend about 90% of their time indoors, so a comfort indoor thermal environment is essential for the satisfaction, productivity and well-being of the building occupants. Assessment of the indoor thermal comfort is the key point for building HVAC system design and operation to provide a comfort indoor environment to building occupants. Predicted Mean Vote (PMV) model is the most widely used tool for the indoor thermal comfort assessment. In this study, the application of the PMV model in Qatar with dry, subtropical desert climate is evaluated. An experiment was conducted in an office building in Doha, Qatar to reveal the occupant perception of indoor thermal comfort. Using collected data, the PMV indexes were calculated using Fanger’s theory and compared with the Actual Thermal Sensation (ATS) of the occupants to assess the applicability of the PMV model to predict the indoor thermal comfort in air conditioned buildings in the climate zone of Qatar. The corresponding occupants’ satisfaction level with the indoor thermal comfort and their adaptive behavior were also assessed.

Energy saving potential of heat removal using natural cooling water in the top zone of buildings with large interior spaces

Generally, ventilation with outdoor air is used to directly remove heat in the top zone of large-space buildings to conserve energy. However, this will increase the latent cooling load because a large amount of humidity can be introduced to the interior when the outdoor air is humid. Therefore, a new method that incorporates a natural cooling water system in the top zone and does not introduce moisture is proposed in this study. The cooling tower as the source of natural cooling water and dry fan coil units (FCUs) as the terminal of removing heat were selected as an example of this new method. In order to analyze the energy saving potential of the new method, 9 cases involving different heat source distributions and cities were simulated by CFD, and 3 more cases with the traditional method were discussed. The results show that the traditional method increases the system energy consumption when the outdoor air humidity is high, and the biggest growth rate is 57.4%. But, the new method can be applied in different cities and in different heat source distributions, and can achieve a considerably high energy saving rate, ranging from 5.2% to 21.4%. The energy saving rate increases as the heat source ratio between the bottom zone and top zone decreases, because more heat can be removed by the dry FCUs. The energy saving rate varies by city, due to the different cooling water temperature. This new method will help guide the design of HVAC systems in large-space buildings.

Integrated maps of risk assessment and minimization of multiple risks for artworks in museum environments based on microclimate control

The design of HVAC systems for museum exhibition rooms is a challenging issue, as artworks require specific hygrothermal conditions to prevent deterioration: on one hand, technical equipment should be able to maintain optimal microclimate, even in critical conditions (e.g., high visitors' presence); on the other hand, energy inefficiency due to oversized system should be avoided. Specifications and guidelines provide hygrothermal values for several typologies of artworks, but the suitability of these values has not been checked through risk assessment methods.In this work, risk assessment models are used to verify the suitability of hygrothermal values suggested by in-force specifications for three artifacts typologies, i.e. paper, panel paintings and wooden sculptures. Results show that current values are suboptimal for two artwork types. Consequently, a procedure for the artwork risk minimization is applied to identify new suitable hygrothermal values for panel paintings and wooden sculptures.The application of these risk assessment methods is also useful in the characterization of actual microclimate in museum exhibition rooms, through the analysis of monitored data. Moreover, risk assessment methods can be used together with suitability indexes of microclimate performance to assess actual microclimate suitability or evaluate risks in indoor environment dynamic simulations.This procedure can be useful for the decision-making community to provide artwork-depending optimal hygrothermal values for museum environments to professionals. Furthermore, it can also be applied by technicians to obtain reference values to minimize risks and, if possible, achieve additional objectives (e.g., energy savings, human thermal comfort).

Application of Green Idea in Energy-Saving Design of Building Hvac System

Application of Green Idea in Energy-Saving Design of Building Hvac System

Life-cycle cost and benefit analysis of utilizing hoods for light-duty cooking appliances in commercial kitchens (RP-1631, part 2)

The objective of this study was to compare the life-cycle cost of using a dedicated hood exhaust and replacement air system versus the cost of removing heat and moisture by the kitchen's general HVAC system. With measured sensible and latent heat generation data from Part I of the RP-1631, whole-building energy performance simulations and cost–benefit analysis were conducted for a generic prototype model of restaurants/cafeteria that included a dining and kitchen zone. Simulations were performed for 12 climate zones in the United States and different amounts of transfer air from the dining to the cooking zone. For most of the climates simulated, the hooded cases resulted in an increase in energy consumption, particularly for the heating-dominated regions, since the heat from the appliance was not used for space heating. In the cooling dominated regions, the hooded cases had about the same or less energy consumption due to reduced cooling loads. However, after integrating the initial cost, maintenance cost, and operating cost in a 10-year lifespan, utilizing a hood with 100% TR always gave the lowest life-cycle cost. This is a result of the lower operating cost compared to the unhooded case and no need for a makeup air system, saving in both equipment and operating cost, compared to the other hooded cases. The study fills a knowledge gap on the impact of commercial kitchen HVAC system design on the energy consumption and life-cycle-cost with realistically measured data of heat and moisture generation from electric counter-top cooking appliances. Also, the potential impact of the hood's capture efficiency on the thermal comfort and indoor air quality was analyzed.

The Prediction of Fuel and Energy Consumption by Using Degree-days Method for Residential Buildings in Denizli

Energy analysis has an important role on optimum design of HVAC systems of buildings. Although there are different energy analysis methods, degree-days method is the easiest and the most reliable one for energy analysis of residential buildings. The main objective of this paper is to present case study for the prediction of total coal and energy consumption by using degree-days method for Denizli, Turkey. On degree-days method, hourly temperature values were used in order to obtain more definite results. This paper is considered at two steps. In the first step, depending on the number of residences, total coal and energy consumptions for uninsulated buildings were predicted for 16, 18, 20, and 22°C base temperatures in 2010, 2015, 2020 and 2023. For the second step, assuming the buildings are insulated (polystyrene for external wall and glass wool for roof), total coal and energy consumptions were predicted for the same base temperatures in the same years. The total coal consumption of insulated buildings for 22°C base temperatures in 2010 is 29% lower than the prediction of the total coal consumption of uninsulated buildings for 16°C base temperatures in the same year.