Design Of HVAC Systems Research Articles

Replicability of nZEBs on Real Estate Market in Mediterranean Countries

According to the recast of the Energy Performance of Buildings Directive and its target for the large-scale increase of nearly-zero energy buildings, nowadays a challenging task is the definition of standard high performing building types depending on location and specific climate conditions. The widespread replicability of nZEB types on the current real estate market could implement nZEB design scenarios attractive and affordable for construction companies and private investors. In particular, this research focuses on the definition of replicable HVAC system configurations with different features and efficiencies starting from a reference building located in a Mediterranean country. The configurations were applied to CorTau House, an nZEB under construction in Piedmont Region, a typical situation of European Mediterranean country where both winter and summer loads, together with humidity, have to be carefully controlled. Building envelope and HVAC system design were matched in order to optimize energy performance and indoor thermal comfort. The HVAC configurations, able to meet nZEB targets and to ensure optimal indoor comfort conditions, were combined with a performing building envelope, made of local construction materials, in order to assess which of them is more energy effective and economically viable. Cost-optimal types were identified and prospective replicability on building market was speculated. Finally, differences between private investor's and company construction's perspectives were discussed.

Energy Modeling for NZEBs: A Case-study

The paper describes the dynamic energy modeling activity performed to achieve a n+NZEB (at the same time Net and Nearly Zero Energy Building), starting from the early design stage to the construction management.The modeling tool IES <VE> has been used to assist the strategy planner in the definition of the sustainability targets and the specialists in the detailed design of HVAC system, glazed façade and lighting equipment. Then, the energy model has been updated after every variation occurred during the construction phase and the results of the dynamic simulation have been checked to guarantee the energy performances forecasted.The paper emphasizes the choices taken in the energy model build-up, with a peculiar focus on simplifications applied. Also, the interactions between different assessment tools is discussed.

Discussion on Energy-Saving Design Measures of HVAC

&lt;p&gt;With continual increase of people's living quality requirements, the demand for buildings with HVAC systems is growing. As energy shortage intensifies today, EEBs (Energy-efficient Buildings) are becoming the main trend of future developments in the construction industry. Therefore, further improving HVAC energy-saving measures is a particularly important task and is the key issue being examined by current HVAC designers. This study starts with analyzing existing problems in energy-saving design of HVAC, and proposes some views and recommendations for HVAC energy-saving design method, as well as reasonable choices of parameters for HVAC systems such as energy-saving design of cooling and heating ventilation, energy-saving design of hot and cold water systems, and optimum heat recovery design of HVAC systems, in order to reduce buildings’ energy consumption and to improve energy efficiency for energy-saving purposes. &lt;/p&gt;

Discussion on Energy-Saving Design Measures of HVAC

&lt;p&gt;With continual increase of people's living quality requirements, the demand for buildings with HVAC systems is growing. As energy shortage intensifies today, EEBs (Energy-efficient Buildings) are becoming the main trend of future developments in the construction industry. Therefore, further improving HVAC energy-saving measures is a particularly important task and is the key issue being examined by current HVAC designers. This study starts with analyzing existing problems in energy-saving design of HVAC, and proposes some views and recommendations for HVAC energy-saving design method, as well as reasonable choices of parameters for HVAC systems such as energy-saving design of cooling and heating ventilation, energy-saving design of hot and cold water systems, and optimum heat recovery design of HVAC systems, in order to reduce buildings’ energy consumption and to improve energy efficiency for energy-saving purposes. &lt;/p&gt;

Thermal comfort in air-conditioned buildings in hot and humid climates--why are we not getting it right?

While there are plenty of anecdotal experiences of overcooled buildings in summer, evidence from field studies suggests that there is indeed an issue of overcooling in tropical buildings. The findings suggest that overcooled buildings are not a consequence of occupant preference but more like an outcome of the HVAC system design and operation. Occupants' adaptation in overcooled indoor environments through additional clothing cannot be regarded as an effective mitigating strategy for cold thermal discomfort. In the last two decades or so, several field studies and field environmental chamber studies in the tropics provided evidence for occupants' preference for a warmer temperature with adaptation methods such as elevated air speeds. It is important to bear in mind that indoor humidity levels are not compromised as they could have an impact on the inhaled air condition that could eventually affect perceived air quality. This review article has attempted to track significant developments in our understanding of the thermal comfort issues in air-conditioned office and educational buildings in hot and humid climates in the last 25 years, primarily on occupant preference for thermal comfort in such climates. The issue of overcooled buildings, by design intent or otherwise, is discussed in some detail. Finally, the article has explored some viable adaptive thermal comfort options that show considerable promise for not only improving thermal comfort in tropical buildings but are also energy efficient and could be seen as sustainable solutions.

Exergy analysis of parameter unmatched characteristic in coupled heat and mass transfer between humid air and water

Systematic analysis of heat and mass transfer processes will help researchers better understand the characteristics of heat and mass transfer and improve the design of HVAC systems and equipment. Throughout the heat and mass transfer process, thermal and humid exergy destruction are separated, which illuminates the relationship of heat transfer and mass transfer. Exergy destruction caused by the inlet parameters of humid air and water and by the flow rate ratio of air to water will not be eliminated by increasing heat/mass transfer area. A parameter unmatched coefficient can be defined to evaluate the influence of inlet parameters quantitatively. Exergy destruction decreases if humid air entering the air–water contact module is close to the saturated line, when the parameter unmatched coefficient is close to 0. The parameter unmatched coefficient was applied to illustration examples of a humidifier and an indirect evaporative cooling tower. Flow paths show better performance when the parameter unmatched coefficient is small.

Building design and operational choices that impact indoor exposures to outdoor particulate matter inside residences

Much of human exposure to particles of outdoor origin often occurs inside homes where we spend most of our time. This work (1) reviews existing literature on the important parameters governing the infiltration and persistence of particles of outdoor origin in residences, (2) re-analyzes portions of data from recent experimental investigations of submicron particle infiltration and central HVAC system operation in single-family homes, and (3) combines these data to highlight particularly stark differences in particle infiltration factors and human exposures to submicron particles of outdoor origin that are driven by building envelope design, filter choice, and HVAC system design and operation (with an additional focus on data from one low-energy home). Results reveal that envelope design and construction, HVAC filter selection, and HVAC system operation can lead to variations in infiltration factors for submicron particles ranging by a factor of 60 or more from the most protective homes to the least protective homes. Moreover, an additional experiment performed in the most protective low-energy home (when relying on infiltration for ventilation air) was also responsible for the highest amount of outdoor particle infiltration when tested again while using an energy recovery ventilator connected to an outdoor air supply for ventilation air, suggesting that residential mechanical ventilation systems can adversely influence outdoor particle infiltration if improperly installed.

Effect of Thermal Plume on Personal Thermal Comfort in Displacement Ventilation at One Side of the Room

The Indoor Zero-Equation Turbulence Model in software Airpak was adopted to simulate the personal thermal comfort in the condition of displacement ventilation at the left side. The parameters of the simulated environment were 25°C and 40%. The simulated results show that over the person, there was a clear phenomenon of thermal plume which entrains the around air resulting in the decrease of the temperature with the increasing of the height. As for the predicted mean vote (PMV) and the percent person's dissatisfied (PPD), their gradient were depended on the temperature distribution formed by thermal plume, and the average value was 0.249 for PMV and 7.25% for PPD. All these show that the effect of thermal plume can not be neglected in the design of HVAC system.

Assessment of condensation of water vapor in the mixing chamber by CFD method

The analyzed topic belongs to the field of design and operation of HVAC systems, focusing mainly on mixing chambers. The paper deals with problems of condensation and freezing of water vapour on walls of mixing chambers in a special case, when the partial pressure of the final resulting state of the mixture of warm moist air and colder air is located above the saturation limit. Experimental in situ methods and computer computational fluid dynamics (CFD) modelling method were used for processing. The main contribution of this work is the finding that partial condensation and freezing of water vapour may occur in local parts of the mixing chamber. It causes problems in terms of hygienic safety and service life of these devices. In particular it has been found that condensation and freezing of water vapour may occur even if relative humidity of the resulting mixture is about 70 %.

Design criteria of built thermal environment for Hot Summer & Warm Winter zone of China

Driven by guiding passive architectural design and HVAC system design, the present study is aimed to propose design criteria of built thermal environment for Hot Summer & Warm Winter zone of China. During the four years from 2008 to 2012, thermal comfort field studies were conducted on 32 urban buildings and 270 rural buildings, more than 500 persons were involved and 3894 sets of raw data that contain thermal acceptability, thermal behaviors and physical parameters were collected. Data of using split air-conditioners was also collected in living rooms, bedrooms and dorms. Based on the data, the acceptable range was determined for environments of naturally ventilation, using fans and using air-conditioners respectively, and accordingly the design criteria of built thermal environment were proposed. The 80% acceptable range of indoor air temperature for naturally ventilated spaces was specified as 18.0–29.5 °C for urban buildings and ≤29.5 °C for rural buildings under the air speed conditions provided by opening windows and using fans. The upper limit of the range can be raised by 1–2 °C by effectively improving indoor humidity and radiation conditions through architectural design. The setting conditions for air-conditioned spaces were obtained as indoor air temperature of 24–28 °C and relatively humidity of 50–70%. The proposed criteria provide solid and essential bases for passive and active designs of built thermal environment in Hot Summer and Warm Winter zone of China.

Thermal comfort: Design and assessment for energy saving

Thermal comfort is one of the most important aspects of the indoor environmental quality due to its effects on well-being, people's performance and building energy requirements. Its attainment is not an easy task requiring advanced design and operation of building and HVAC systems, taking into account all parameters involved. Even though thermal comfort fundamentals are consolidated topics for more than forty years, often designers seem to ignore or apply them in a wrong way. Design input values from standards are often considered as universal values rather than recommended values to be used under specific conditions. At operation level, only few variables are taken into account with unpredictable effects on the assessment of comfort indices. In this paper, the main criteria for the design and assessment of thermal comfort are discussed in order to help building and HVAC systems designers and operators to navigate the complex and varied world of standards in the field of thermal environment for improving indoor environmental quality and energy saving. The examples discussed in the paper will also be useful for the standardization, leading to harmonized documents more readable for all users.

Optimization of the HVAC system design to minimize primary energy demand

Abstract The purpose of this study is to propose an optimal design method for the HVAC system in apartment using a genetic algorithm and to examine the possibility for the energy conservation of a designed HVAC system. The energy demand for cooling and heating in apartment house is determined by using TRNSYS. By a modified genetic algorithm called multi-island genetic algorithm, the optimal running pattern of HVAC systems is decided to minimize the energy consumption. An optimal design method for the HVAC system of the apartment house was proposed using both genetic algorithm and data of cooling/heating demand load simulated by TRNSYS. It has been confirmed that energy for equipment systems in apartment house can be saved by using operation plan of HVAC systems. The results show that this proposed method is significantly capable of determining optimal system design for saving energy in apartment house. We will perform the design of HVAC system considering an initial cost, a running cost and emission of CO2, and so on in the future.

Comprehensive Analysis and Research on the Factors Influencing Energy Efficiency and Consumption of Public Buildings

A public building of Jiangsu Province is analyzed by DeST software based on the coupling relationship of building envelope, natural ventilation, lighting and natural lighting, and HVAC system, and the annual heating and cooling loads and power consumption of design building and benchmark building are calculated. After fully taking into account coupling relationship of all factors, a reasonable choice of design parameters, the design of HVAC system is optimized, achieving the goal that total energy consumption of design building is less than 80% of specified value of energy efficiency by national and local standards.

A novel artificial bee colony algorithm for HVAC optimization problems

The strategy of simulation-optimization is popular in handling the design and energy management of centralized HVAC systems. An effective optimization algorithm is paramount to obtain the optimal design and operation of HVAC systems. Due to the multi-dimensional and highly constrained nature commonly found in HVAC problems, traditional optimization methods are generally not applicable. Instead, a metaheuristc algorithm, e.g., the genetic algorithm, is a good choice to achieve these purposes. In recent years, the paradigm of the artificial bee colony is emerging in the field of evolutionary computation. The artificial bee colony optimizes the problem through the foraging behavior of honey bees. This article presents a novel approach developed from this paradigm, called the one-position inheritance artificial bee colony algorithm, for handling HVAC system optimization. Through two HVAC example problems, it is found that the one-position inheritance artificial bee colony can more effectively and efficiently search the optimal solutions against the genetic algorithm and original artificial bee colony. This suggests that the one-position inheritance artificial bee colony is a good optimization algorithm to solve other HVAC engineering problems with a multi-dimensional, mixed discrete-continuous, and highly constrained search landscape.

Simplified optimization method for preliminary design of HVAC system and real building application

HVAC systems (heating, ventilation, and air conditioning) are recognized as the greatest energy consumers in commercial and institutional buildings. Generally, designers use common sense, historical data, and subjective experience in designing these systems; this includes the number of systems chosen and the grouping of the zones served by these systems. HVAC energy efficiency is not an easily calculable criterion during the selection of these systems; usually the first selection criterion is the weakest investment cost. In this article, we present a simplified optimization method for preliminary design of HVAC system using the zones’ daily profile loads. A global load ratio is applied as an optimization function. The global load ratio represents the relationship between the system's real load and its possible maximum load for a given period. The variables for the optimization problem are: (i) grouping of the zones served by the systems and (ii) number of systems serving the building. Type of system was preselected for the present study, but this could also serve as an optimization variable. The correlations between global load ratio and energy consumption were shown using an office building. Then, this method was applied on an existing institutional building and compared with the detailed optimization method. In the second method, the HVAC energy consumption, calculated using DOE-2 software, was used as the optimization function. The comparison made among the existing, reference, and optimized buildings (all sharing the same constraints) have yielded significant energy savings for HVAC energy consumption. A life cycle cost analysis has also been done to estimate savings in terms of investment, operation and maintenance costs. These savings depend upon building configuration, the constraints imposed, the types of HVAC systems selected, and the control strategies for these systems.

Strategies for Reducing Energy Consumption in a Student Cafeteria in a Hot-Humid Climate: A Case Study

Increasing attention is being given to energy consumption and potential for energy savings in public buildings in order to improve energy performance. Due to their size and functional requirements, public buildings especially cafeteria facilities tend to consume a significant amount of energy. Furthermore, due to their operational characteristics and construction pattern, unnecessary energy is likely to be used for maintaining acceptable indoor environmental quality. In this study, a student cafeteria at King Fahd University of Petroleum and Minerals, Saudi Arabia, was selected for the assessment of its energy performance and potential energy conservation opportunities. Energy simulation software Visual DOE 4.1 was used to develop an energy performance model for assessing various energy conservation measures pertinent to the building envelope and HVAC system design. Data required for setting up the model were gathered through simple energy audits. The architectural and mechanical drawings and the history of electrical consumption were collected. Various energy conservation strategies were then implemented including standards, single and combined energy conservation measures. These measures resulted in a combined design saving of 27.4%, the HVAC system saving 10.6%, implementation of standards saving about 16.7%, lighting 6.6%, equipment 2.6%, insulation 2.5% and glazing 1.4%. Based on these results, it is apparent that there is a significant potential for improving energy performance and justification to employ the suggested measures for achieving substantial energy savings and minimize energy consumption.

Operational Heat Balance Model with Parameterized Geometry for the Prediction of Car Cabin Heat Loads

The paper presents the development of a mathematical model and a simulation tool for the transient prediction of the indoor climate and the heat loads in a car cabin, under real operating conditions. The main objectives were to develop a tool which facilitates, for example, the design of a cabin HVAC system or an on-line control. The model is based on the energy balance between the cabin and the outdoor environment accounting for conduction, convection and shortwave and longwave radiation. Inside the car cabin, the heat exchange is calculated between the human body, the air zone, the interior cabin surfaces and the incoming air from the HVAC system. The heat balance model assumes a simplified 3D geometry of a cabin, which is specified by seven basic parameters. The model also allows simulating the incidence angle of the sun rays onto the individual parts of the exterior surface during parking as well as during a journey. The model was tested and evaluated for a Škoda Felicia Combi car in situations of summer parking and an autumn journey. Measured data were used both as boundary conditions for the model and as validation and calibration data. The air temperature inside the car cabin, predicted by the model, was in a very good agreement with the measured mean air temperature. The model is able to correctly predict the indoor cabin air temperature and the heat loads into the car cabin, thus it is well suited as a software support tool in the process of HVAC design and on-line cabin climate control.

Critical review on hospital surgical room and mechanical system designs

The design of HVAC systems for surgical operating rooms requires specific guidance for the design engineer in order to insure that thermal comfort and sepsis control are maintained at all times in order to protect the occupants of the room. Operating room ventilation has been through significant design improvements from the beginning of the 20th century until now. Researchers have found that the room air distribution pattern is a critical parameter for airborne sepsis control, as most contaminants are introduced into the operating room by occupants and object within the room. Computational models have been used by many researchers to determine the room air distribution patterns for a variety of ventilation system and room configurations, but few of these models have been validated with experimental data. Further research is needed to both validate the models that are used for understanding the role of air distribution patterns in surgical sepsis control, as well as studying the impact of increasing heat loads in the next generation of surgical procedures.

Designing HVAC systems using particle swarm optimization

Many design and operating goals in HVAC systems are optimization problems. For example, building operators want to determine the combination of equipment and set-points that result in the most energy-efficient operating conditions. Similarly, HVAC system designers want to determine the best combination of equipment, components, and operating conditions that provide minimum lifecycle cost. In both problems, the goal is to find an optimal set of system design variables. The purpose of this work is to apply an optimization technique known as particle swarm optimization to the design and operation of HVAC systems. This algorithm is based on the idea of swarms of animals, such as flying birds or insects, searching for food. In these swarms, each member gains knowledge from the whole and in turn contributes its individual knowledge back to the swarm. The result is a very efficient way to find the best available food source. The particle swarm optimization algorithm is well suited to computers with multiple processors and to HVAC problems, because it does not require continuous or well-behaved mathematical functions. Another advantage of the method is that it is remarkably simple to implement. This article illustrates the particle swarm optimization algorithm by applying it to the design of an HVAC piping system.

공조방식에 따른 사무소 건물의 에너지 성능 평가

ABSTRACT:High economic growth causes increase of the building energy consumption. The energy consumption for HVAC system accounts for 40∼50% of the whole building consumption. The trend for building is large-scale and high-rise. Because of the trend, the energy consumption is becoming bigger than before. Nowadays, HVAC system design are recognized as the solution for a energy-saving. This paper is focused on the energy performance evaluation of central air- conditioning system(water-based) and system air-conditioning that were applied to the office building. The systems are modeled and simulated by using EnergyPlus Software 6.0. After the Simulation, annual cooling and heating energy consumption were calculated. It was found that the system air-conditioning can reduce the energy consumption approximately 55.24% annually compared with the central air-conditioning system(water-cooled). In addition, about 46.13% of annual operating costs can be reduced by use of system air-conditioning.Keywords:Energy consumption(에너지 소비량), System air-conditioning(시스템 에어컨), Energy performance evaluation(에너지 성능평가), Operation cost(운전비용)