Experimental investigation of a novel desiccant cooling system

Desiccant based air conditioning systems are a suitable way to improve indoor air quality due to its superior humidity control. In this study, a novel desiccant based air conditioning system is designed and tested experimentally to improve the indoor air quality and reduce energy consumption. In the system studied, a heat exchanger, which is not used in this type of systems, for pre-heating the regeneration air with exhaust air is used. This paper reports results of initial operation and operational procedures. The performance of the system and its components is discussed.     

Predictions of energy savings in HVAC systems by lumped models

An approach to optimizing the energy efficiency of a Heating, Ventilating, and Air Conditioning (HVAC) system is presented that utilizes computational predictions of the effect of heat load distribution on moist air temperature, density, and humidity variation. Lumped-HVAC (L-HVAC) is a new lumped parameter code that couples fluid transport, energy transport, thermodynamics, and psychrometrics in an HVAC system. This code contains a nonlinear implicit solution algorithm for steady-state and transient calculations for flow resistance, water mass balance, and energy conservation. L-HVAC has been validated using a simplified analytical model, the commercial lumped parameter code SINDA/FLUINT, and experimental measurements. Steady-state calculations for a single-room system suggest an order of magnitude greater energy savings using a variable chiller power control approach compared to control damper and variable-drive fan approaches. L-HVAC was also applied to predict that the fraction of latent to total heat load influences the steady-state system temperature by up to 0.4 °C for the example system in this study.     

浅析高层建筑暖通空调系统选择方法

简述了采暖通风和空气调节的内涵,重点论述了高层建筑暖通空调系统选择、主要设备配置情况及应注意的问题,表明随着科技进步及建筑业的发展,暖通空调技术应不断创新、发展,以适应当前多样化的建筑环境。     

An experimental system for advanced heating,ventilating and air conditioning (HVAC) control

While having the potential to significantly improve heating, ventilating and air conditioning (HVAC) system performance, advanced (e.g., optimal, robust and various forms of adaptive) controllers have yet to be incorporated into commercial systems. Controllers consisting of distributed proportional-integral (PI) control loops continue to dominate commercial HVAC systems. Investigation into advanced HVAC controllers has largely been limited to proposals and simulations, with few controllers being tested on physical systems. While simulation can be insightful, the only true means for verifying the performance provided by HVAC controllers is by actually using them to control an HVAC system. The construction and modeling of an experimental system for testing advanced HVAC controllers, is the focus of this article.     

Simulation of a building and its HVAC system with an equation solver: Application to benchmarking

The today-availability of powerful engineering equation solvers is opening very new possibilities in technical component modelling and in system simulation. The simulation models, the “user guide” and the “reference guide” are all included in a same file. Reliable “reference” and “simplified” models are currently available for the building zone and for most (heating, ventilation and air-conditioning) HVAC components. Focus is given here on “simplified” models and on a simulation tool, called “Benchmark”. This tool should help an auditor to make the best use of the limited information usually available about actual fuel and electricity consumptions and to get a very first evaluation of the actual performances of a given HVAC system. An example of such use is presented. Another simulation tools and more information about the modelling of HVAC components will be presented in a further paper.     

Desiccant wheels as gas-phase absorption (GPA) air cleaners: evaluation by PTR-MS and sensory assessment

Two experiments were conducted to investigate the use of the co-sorption effect of a desiccant wheel for improving indoor air quality. One experiment was conducted in a climate chamber to investigate the co-sorption effect of a desiccant wheel on the chemical removal of indoor air pollutants; another experiment was conducted in an office room to investigate the resulting effect on perceived air quality. A dehumidifier with a silica-gel desiccant wheel was installed in the ventilation system of the test chamber and office room to treat the recirculation airflow. Human subjects, flooring materials and four pure chemicals (formaldehyde, ethanol, toluene and 1,2-dichloroethane) were used as air pollution sources. Proton-Transfer-Reaction--Mass Spectrometry (PTR-MS) and sensory subjects were used to characterize the effectiveness of chemical and sensory pollution removal of the desiccant wheel. The experiments revealed that all the measured VOCs were removed effectively by the desiccant wheel with an average efficiency of 94% or higher; more than 80% of the sensory pollution load was removed and the percentage dissatisfied with the air quality decreased from 70% to 20%. These results indicate that incorporating a regenerative desiccant wheel in a ventilation system is an efficient way of removing indoor VOCs. PRACTICAL IMPLICATIONS: This study may lead to the development of new air cleaners and validates a new concept for the design of ventilation systems that can improve indoor air quality and reduce energy consumption.     

Performance testing of a counter-cross-flow run-around membrane energy exchanger (RAMEE) system for HVAC applications

A novel run-around membrane energy exchanger (RAMEE) system is designed, built, and tested for heating, ventilating, and air-conditioning applications. The RAMEE system consists of two counter-cross-flow liquid-to-air membrane energy exchangers, one located in the supply and the other in the exhaust air streams of a building. Inside each exchanger, a micro-porous membrane separates the air and desiccant solution streams. This membrane allows heat and water vapor exchange between the two streams. The RAMEE system thus exchanges sensible and latent energy between the supply and exhaust air streams by using a desiccant solution as the energy carrier that is pumped in a loop between the two exchangers. The RAMEE performance is evaluated by testing the system with various air and desiccant solution flow rates during standard summer and winter operating conditions. During summer test conditions, the total system effectiveness increases with increasing desiccant flow rate, but decreases as the air flow rate increases. Under winter test conditions, the total effectiveness changes little with changes in the air and desiccant flow rates. For some test conditions, the maximum total effectiveness of the system is between 50 and 55%. The effectiveness data are compared to available correlations and reasons for discrepancies are discussed.     

济南某商场空调系统测试与能耗分析

对济南某商场空调系统运行状况进行了测试与调研,分析了该空调系统的运行效率、耗能状况,提出了整改建议,为节能改造方案提供了基础数据.     

微型燃气轮机热电冷三联产系统总能分析及能效特性实验研究

对以微型燃气轮机为核心的冷热电三联产系统进行总能分析,并对其能效特性和在部分负荷时的能效特性进行实验研究。从总能分析和能效特性的实验研究中,可以得出当负荷变小时,总能效率会明显下降,系统的能效特性变差,这一变化规律可为以后的冷热电三联产系统的研究借鉴。     

A new local pressure loss coefficient model of a duct tee junction applied during transient simulation of a HVAC air-side system

Most of the local pressure loss coefficient (LPLC) models for duct fittings used in heating, ventilation and air conditioning (HVAC) air-side system transient simulations are simplified. The LPLCs are defined as having a constant value at the rated flow condition or as having a polynomial function of the flow ratio (or velocity ratio). To determine the influence of these simplifications, this study used a diverging tee junction as an example. First, we performed CFD calculations to generate a new LPLC dataset and trained a data-driven model using feature weighted support vector regression (FWSVR) combined with particle swarm optimization (PSO-FWSVR). Finally, we compared this new LPLC model with the two traditional models at the level of both individual junction and air-side system. The results show that the accuracy of the new model is greatly improved and the LPLC model can have a significant impact on the system operation condition.     

Development of HVAC system simulation tool for life cycle energy management Part 1: Concept of life cycle energy management and outline of the developed simulation tool

The importance of LCEM (life cycle energy management) has been recognized from the view of life cycle energy savings for sustainable buildings. The purposes of this research are the proposal of an LCEM framework and development of prototype HVAC system simulation tools for LCEM. In this paper, the necessity of energy simulation tools for LCEM is discussed, and the outline and solution method of the simulation tool are shown.     

Economical assessment of different HVAC systems for an operating room: Case study for different Turkish climate regions

In this study, the annual energy consumptions of four different heating, ventilation and air conditioning (HVAC) systems serving to operation rooms (ORs) located at five different cities (Izmir, Antalya, Istanbul, Ankara and, Erzurum) in Turkey are analyzed. The study is performed for four different HVAC systems: (a) 100% fresh air system (System I), (b) 100% fresh air with half air volume rate at night period (System II), (c) 100% fresh air with half air volume rate at night period and heat recovery unit (System III), (d) 50% fresh air with half air volume rate at night period and with heat recovery and mixing units (System IV). Life cycle cost (LCC) for 20 years life span is calculated for the considered systems. It is found that System IV considerably reduces energy consumption and it is economically proper for the considered cities. The rate of energy consumption and LCC reductions are greater for the cities with extreme climate condition having relatively low specific humidity ratio. Using System IV instead of System I reduces OR energy consumption by 74% for the city of Erzurum which has a cold and dry climate.     

Development of dual-source hybrid heat pump system using groundwater and air

To achieve high heat pump efficiency, groundwater heat pump (GWHP) system uses groundwater, which is relatively stable AT temperature compared with outdoor air, as a heat source. However, it is difficult to meet annual heating and cooling loads using only groundwater as a heat source. In order to optimize the operation method of GWHP systems, it is necessary to develop a system utilizing both groundwater and air sources according to the building load conditions. Furthermore, during intermediate seasons (such as spring and autumn) with reduced heating and cooling loads, GWHP system is less efficient than air source heat pump (ASHP) system according to temperature conditions. In order to more efficiently use GWHP systems, it is necessary to develop a system which utilizes both groundwater and air sources according to temperature conditions and building loads. This research has developed a GWHP system that employs a hybrid heat pump system with groundwater wells using dual groundwater and air heat sources. In this paper, the annual performance of the developed system has been calculated, and several case studies have been conducted on the effect of introduction location, refrigerant and pumping rate. Furthermore, the coefficient of system performance and the effects on underground environments have been evaluated by real-scale experiment using two wells.     

Energy efficiency and economic feasibility analysis of cogeneration system driven by gas engine

A cogeneration system driven by gas engine is proposed and studied. The cogeneration system can provide electricity generation and cooling/heating for buildings. The cogeneration system has a large potential for energy saving and economical benefits. Primary energy rate (PER) and comparative primary energy saving are used to evaluate and compare the performances of the cogeneration system and conventional separate system. The comparative primary energy saving of the cogeneration system is more than 37% compared to conventional separate system at the required energy flows. The total annual income, the total annual saving and payback period of the cogeneration system are used to analyze its economy. The calculation result of economic analysis shows that the cogeneration system has a good economic benefits.     

厦门某影剧院空调设计及分析

介绍该影剧院的空调系统配置,并结合建筑本身的特点及空调区域功能要求介绍舞台及观众厅的空调气流组织形式、通风系统设计及消防排烟系统设计特点。     

Removal of submicron particles using a carbon fiber ionizer-assisted medium air filter in a heating,ventilation, and air-conditioning (HVAC) system

Laboratory tests of particle removal were performed with a pair of carbon fiber ionizers installed upstream of a glass fiber air filter. For air flow face velocities of 0.4, 0.6, and 0.8 m/s, the overall particle removal efficiencies of the filter for all submicron particles were 17%, 16%, and 14%, respectively, when the ionizers were not turned on. These values increased to 27%, 23%, and 19%, respectively, when the ionizers were used to generate ions of 6.0 × 10⁹ ions/cm³ in concentration. The carbon fiber ionizers were then installed in front of a glass fiber air filter located in a heating, ventilation, and air-conditioning (HVAC) system. Field tests were performed in a test office room with a total indoor particle concentration of 2.2 × 10⁴ particles/cm³. When the flow rate was 75 cubic meters per hour (CMH), the steady-state values of the total indoor particle concentrations using the glass fiber air filter with and without ionizers decreased to 0.87 × 10⁴ particles/cm³ and 1.15 × 10⁴ particles/cm³, respectively, resulting in a 25% decrease of the ionizer effect. When the operation flow rate was increased to 115 and 150 CMH, the effect of the ionizer decreased to 19% and 17%, respectively. These experimental data match the results calculated using a mass-balance model whose parameters were determined from laboratory tests.     

Experimental investigation of a solar cooling absorption system operating without any backup system under tropical climate

In the last few years, thermal comfort research in summer has significantly increased the electricity consumption in buildings. This is mainly due to the use of conventional air conditioning systems operating with mechanical vapor compression. Solar cooling systems appear to be an interesting solution to solve this problem. But the understanding of this technology has to be refined through fundamental studies by developing numerical simulations. Moreover, the study of pilot plants is a practical method to gain experience by analyzing all the processes behind solar cooling technology. This paper presents an experimental study of a solar cooling absorption system implemented in Reunion Island, located in the southern hemisphere near the Capricorn Tropic. The particularity of this project is to achieve an effective cooling of classrooms, by a solar cooling system without any backup systems (hot or cold). The aim of this experimental study is to define the limits of the use of such system under tropical climate conditions without setting a set point temperature. Indoor thermal comfort is achieved by a self-stabilizing operating system that maintains the indoor temperature 6 °C below the outdoor temperature. During some critical periods of the year, when the outdoor temperature is very high and when the solar cooling system cannot provide enough refrigerating production, thermal comfort inside the building is achieved by using ceiling fans. Firstly we will present the installation and the choices we made in the control and design process. In the second part, an analysis of the experimental results will be presented.     

Stub column tests for racking design: Experimental testing,FE analysis and EC3

The Laboratory of Elasticity and Strength of Materials, in the School of Engineering of Barcelona (UPC), has gained a wide experience in pallet-rack testing in recent years. We have gathered a comprehensive set of experimental results from upright cross-sections subject to compression. Twenty different pallet-rack steel profiles have been tested. This information is valuable and allows us to evaluate different methods alternative to testing as a design option. In this paper, two alternative methods are considered: the analytical, by applying the European Standard EN 1993-1-3:2006/AC:2009; a traditional method, which involves the effective width determination for each part of the section subject to compression; and the numerical, by applying finite element analysis, including non-linear material and geometrical behaviour. The results of both methods are compared to the experimental ones. This research reveals that even though the European Standard EN 15512:2009 does only accept the experimental method for perforated sections, theses other two methods can give good accuracy, and be good tools in the stage of design and optimization.     

Variation in indoor particle number and PM2.5 concentrations in a radio station surrounded by busy roads before and after an upgrade of the HVAC system

Indoor particle number and PM_2.5 concentrations were investigated in a radio station surrounded by busy roads. Two extensive field measurement campaigns were conducted to determine the critical parameters affecting indoor air quality. The results indicated that indoor particle number and PM_2.5 concentrations were governed by outdoor air, and were significantly affected by the location of air intake and design of HVAC system. Prior to the upgrade of the HVAC system and relocation of the air intake, the indoor median particle number concentration was 7.4×10³ particles/cm³ and the median PM_2.5 concentration was 7 μg/m³. After the relocation of air intake and the redesign of the HVAC system, the indoor particle number concentration was between 2.3×10³ and 3.4×10³ particles/cm³, with a median value of 2.7×10³ particles/cm³, and the indoor PM_2.5 concentration was in the range of 3–5 μg/m³, with a median value of 4 μg/m³. By relocating the air intake of the HVAC, the outdoor particle number and PM_2.5 concentrations near the air intake were reduced by 35% and 55%, respectively. In addition, with the relocation of air intake and the redesign of the HVAC system, the particle number penetration rate was reduced from 42% to 14%, and the overall filtration efficiency of the HVAC system (relocation of air intake, pre-filter, AHU and particle losses in the air duct) increased from 58% to 86%. For PM_2.5, the penetration rate after the upgrade was approximately 18% and the overall filtration efficiency was 82%. This study demonstrates that by using a comprehensive approach, including the assessment of outdoor conditions and characterisation of ventilation and filtration parameters, satisfactory indoor air quality can be achieved, even for those indoor environments facing challenging outdoor air conditions.     

Experimental study of a ground sink direct cooling system in cold areas

A conception with ground as a heat sink directly for cooling of the buildings in cold areas is presented. A corresponding experimental system was constructed in Harbin area and operated in summer in 2006. Some important performance parameters, such as the cooling seasonal performance factor (CSPF) and the average heat rejection rate unit depth of borehole, were obtained and some analyses for the system characteristics are made. The experimental results show that the ground sink direct cooling system (GSDCS) presented has great potentialities in energy saving within a specified region.