An automotive air conditioning and heat pump (AAC/AHP) system employing refrigerants R134a and R1234yf was developed and tested in cooling and heating operation modes under broad ranges of compressor speed and air inlet temperature conditions. Using test results, various energetic and exergetic performance parameters of the system were evaluated and compared. The R1234yf system provided on average

The main objective of this study is to determine the optimum insulation thickness of residential buildings in Turkey, under the influence of cooling and heating loads by life cycle cost analysis (LCCA). 5-storey apartment building with an Area/Volume ratio (A/V) of 0.40 m−1 and 10-storey apartment building with an A/V ratio of 0.32 m−1 are taken as reference buildings. The annual energy needs are calculated

A novel dataset based on satellite observations of aircraft positions was utilized to estimate normal accelerations of commercial aircraft during climb and descent legs. Further, these accelerations are used to simulate the effects on exposure to expiratory airborne contaminant inside commercial aircraft cabins. Compared to previous studies, which reported exposures more than twice due to high aircraft

There are no ASHRAE/HVI standards for characterizing or specifying acceptable values of capture efficiency (CE) (i.e. percentage of cooking-contaminants captured/exhausted by a household rangehood). A test method, ASTM-E3087.18, was recently published describing a facility/procedure for attaining consistent CE measurements. This study presents the design, construction and operation of the first CE

Combined district heating (DH) systems have at least one base load heat plant and several peak shaving heat sources, which can be installed in primary network or in the heating substations. This paper studies the combined DH system with peak shaving gas-fired boilers in heating substations, where the peak boilers can be connected to the heat exchangers with series or parallel mode. We analyze the thermal

Building energy estimation for the building sector under various scenarios are needed for building energy regulation and policy making. This often starts with representative baselines (either empirical baseline or modeled baseline). Commercial Buildings Energy Consumption Survey (CBECS) data is a widely used empirical baseline for U.S. commercial buildings, but none of the existing baseline model are

This paper presents a near-optimal control algorithm for minimizing energy costs in hybrid cooling plants in response to cooling loads. The approach is based upon an approximate solution to the partial differential equations involved in minimizing the cost of energy consumed by the plant with respect to two control variables: cooling tower air flow and condenser water flow. The parameters of the algorithm

Public attention has been drawn to the commercial restaurant cooking emission since it can cause health and hygiene risks, reduction of the efficiency of the ventilation system, and even fire accidents. The attempt of including the Ultraviolet-C (UVC) lamps with Type I hood has the potential to reduce the grease deposition on the ductwork and pollution in the exhaust by oxidizing the emissions. A method

Chillers consume considerable energy in building HVAC systems, and the optimal operation of chillers is essential for energy conservation in buildings. This paper proposes a model-free optimal chiller loading (OCL) method for optimizing chiller operation. Unlike model-based OCL methods, the proposed method does not require accurate chiller performance models as a priori knowledge. The proposed method

Energy can be recovered from building exhaust via water vapor transport and heat transfer across gas permeation membranes, thereby reducing latent and sensible loads during both heating and cooling seasons. The process known as membrane-based energy recovery ventilation (ERV) has been commercialized by several HVAC manufacturers, but so far has mostly been offered in flat sheet membrane configurations

(2020). Flammable refrigerant safety. Science and Technology for the Built Environment: Vol. 26, Flammable Refrigerant Safety, pp. 587-587.

The aim of this study is to investigate dispersion and deposition characteristics of different particle diameters (0.5-5-10 μm) for a displacement ventilated and floor heated environment, experimentally and numerically. The experiments are performed in a reduced scale model with the operating parameters determined regarding to the similarity. Results are used to validate simulation outputs obtained

Existing studies have treated variable refrigerant flow (VRF) control as a local control problem where control variables are determined using only local state information. This study investigates an integrated VRF control in which the VRF control actions are determined based on not only local information but also the dynamics of the room it serves. For this purpose, two artificial neural network simulation

Sleep is essential for the body to recover from both the physical and psychological fatigue accruing throughout the day, and to restore energy to maintain bodily functions. Bedroom environmental quality is one of the key causes of sleep disturbance, so a better understanding of the associations of bedroom temperature and ventilation rate (using CO2 as the surrogate) with sleep quality is necessary

In recent years, severe and persistent winter haze has appeared more frequently due to coal-combustion heating for residential buildings in the winter in northern China. To solve the problem, the Chinese government proposes to replace coal-combustion heating with electricity-driven air-source heat-pump heating. In this article, the performance of an air-source heat pump was studied for suburban residential

In this study, a detailed modelling applicable for membrane dehumidifying system is proposed. This system contains a membrane module, 2-stage vacuum pumps, a condenser, and a regulating valve. The proposed model does not need any prior setting of the vacuum level of the permeate side, and the predictive results are in line with the benchmark. It is found that the COP (coefficient of performance) is

The existing Fault Detection and Diagnosis (FDD) model of chillers requires considerable normal and fault data. The acquisition of these data is time-consuming and expensive, and the model is only suitable for special units, which makes it difficult to popularize FDD technology in the operation and management of chillers. At present, a 120-ton chiller has only a small amount of normal and fault data

Cooling water (CW) system with strong nonlinear characteristics is a critical component of central air conditioning systems. Further, variable flow control of CW pumps is a critical measure for achieving energy-saving operation of CW systems. Proportional–integral (PI) control algorithm is widely used in the variable flow control of CW systems, and fuzzy control algorithm also plays a significant role

The influence of three ventilation systems, namely, the displacement ventilation system, the stratum ventilation system, and the underfloor air distribution system, on human thermal comfort was investigated at different supply air temperatures. We compared the air velocity, CO2 concentration, temperature, human thermal comfort, and energy utilization coefficient of the three systems at a supply air

This paper presents the application of a multi-agent control methodology to large chiller plants. The approach, originally conceived to automate controller design and reduce engineering costs in building energy systems, consisted of a multi-agent simulation framework with distributed consensus-based optimization algorithms. To adapt the approach to this scenario, agents representing physical components

Particle filters are used in heating, ventilating, and air-conditioning (HVAC) systems to protect equipment and reduce exposure to airborne particles. Filtration standards such as ANSI/ASHRAE Standard 52.2 are used to evaluate filter performance in a laboratory setting. In this work, we examined the lab-tested performance of new filters with different nominal efficiencies as determined by ASHRAE Standard

This paper describes the development of a method that can be used to simulate in a laboratory the effects of air side fouling of condensers from split system air conditioners. The method includes a synthetic fouling agent that realistically mimics field fouling. The fouling agent was developed by considering the fouling materials and effects on heat transfer and air side pressure drop that were measured

Finite-element models were developed to predict the deformation of unreinforced spiral flat oval ducts when subjected to a range of positive/negative internal gauge pressures. The models included the effects of duct self-weight. Deflection predictions resulting from a linear analysis and a nonlinear analysis were contrasted. This study also compared finite-element model predictions to experimentally

HVAC filters are exposed to a diverse mixture of aerosols during their service life. Aerosol physiochemical properties can have a significant impact on the removal efficiency and loading behavior of a filter. New aerosol generation techniques are needed to age HVAC filters with particle size distributions (PSDs) representative of those found in outdoor (urban) and indoor environments. This study evaluated

A common form of particulate air filters is the pleated filter. The pressure drop and particle removal efficiency are the most important performance indicators of this filter. A computational fluid dynamics (CFD) tool was utilized to predict the pressure drop of a two-stage filter cartridge. In the CFD analysis, the flow through the porous medium was used as an indicator of the pressure drop in the

For measurements of unitary HVAC&R equipment and heat exchanger performance, tolerances on capacity measurements relative to the published ratings or mismatch in energy balances are limited to 5% as mentioned in AHRI standards (210/240, 340/360, and 365), ASHRAE 33 and 37, and in U.S. federal regulations. However, differences in design of the air mixing and measuring apparatus due to generous guidelines

Equipment reliability, efficiency, charge migration, and refrigerant charge optimization of refrigeration systems has been widely emphasized as critical development focus. Numerous modeling tools are utilized to predict charge of oil and refrigerant in refrigeration systems during system design. However, there is a lack of experimental validation data to confirm the accuracy of these models. The sampling

In hot arid regions like the UAE, it is of the utmost importance to evaluate and determine the best building orientation. Consequently, the aim of this paper is to investigate thermal performance of building orientations in the UAE. In order to test the thermal performance of building orientations in Sharjah, a real lab-scale house was constructed. It was divided into two zones; one oriented toward

A control-oriented model of an Electrically heated Thermal Energy storage device (ETS) is presented. The ETS consists of bricks heated up to 871 °C with electric coils; heat is discharged with an airflow passing through channels in the bricks. The device stores energy during off-peak periods to meet future on-peak building heating loads. While its rationale is understood, improvement regarding operation

The present study used large eddy simulations (LES) to examine the pedestrian wind velocity distribution for several cases of terraced houses with extensions. Two simulation cases of idealized terraced houses were performed with extension elements in square (E-SQ) and staggered (E-ST) arrangements. These extension elements were treated as secondary roughness. A simulation of the terraced houses without

This paper presents the results of a study investigating the assembly, durability, and leak rate of mechanical joints used in refrigerant and air-conditioning systems. A significant motivating factor of the study is identifying joint types that are suitable for use in systems that employ flammable refrigerants. In the study, three different fitting types were evaluated (press or crimp fittings, compression

Building audits are conducted in many commercial buildings to identify opportunities to reduce energy costs and improve building operation. Because audits require significant effort by building engineers, they are usually only affordable for larger commercial buildings. “No-touch” building audit tools have thus been developed to identify potential savings based on a simplified analysis of building

The main purpose of ventilation system is to meet the requirements of thermal comfort and air quality for the occupants. HVAC designers select air supply devices by using manufacturers’ data, under the assumption that the outflow from the elements is uniform and radially symmetric. Uniformity and symmetry hold only if air velocity vectors have uniform intensities and directions that are perpendicular

With the increased use of flammable refrigerants, there is a need to provide a warning in case of a refrigerant leak that might lead to hazardous conditions. The addition of an odorant has been used for this purpose in other industries and could potentially be used in the HVAC&R industry if suitable odorants could be identified. As an initial step in the evaluation of the use of an odorant, a white

Experiments are performed for outwardly propagating spherical flames of R-32/air mixtures at constant pressure. A high-speed video camera captures shadowgraph images from which the flame radius as a function of time is extracted. Direct numerical simulations with an optically thin radiation model and detailed kinetics are performed to predict the flame radius and study the effects of stretch and radiation

Indoor air quality (IAQ) plays a significant role in human health, and CO2 has a long history of use as an IAQ indicator. Formaldehyde is one of the most ubiquitous indoor pollutants with proven adverse health effects. However, formaldehyde sensors are generally expensive, and they are not as accurate as CO2 sensors. Thus, it is important to determine whether CO2 could be used as an indicator for formaldehyde

This article presents a systematic review of thermal comfort studies in Indian residential buildings, to identify the present research scenario, data gaps, and policy interventions. The majority of the studies were performed in a composite climate (10), followed by a warm humid climate (seven), and a very few from cold (two) and hot and dry (two) climates. None of these thermal comfort studies took

This study conducted experimental measurements of ventilation rates and associated pollutant concentrations in two retail stores for one-week intervals. Pollutants monitored were formaldehyde and total volatile organic compounds. Based on the pollutant measurements and mass–balance modeling, different ventilation rate reduction scenarios were proposed, and for these scenarios the differences in energy

This study investigates the thermal comfort, airspeed and temperature distribution, air change effectiveness and importance of the boundary conditions on the selection and performance of Active Chilled Beams (ACB). Many past studies in cooling confirm that the thermal comfort is satisfactory because the temperature gradient and airspeeds are acceptable at the occupant level without addressing the local

What type of mattress could improve human thermal comfort and sleep quality in hot/cold weather is open questions. In this study, using four different mattresses (temperature-controlled mattress with built-in circulating water pipes, temperature-controlled mattress with built-in integral water cushion, 3D air mesh fabric mattress, and latex foam mattress), a series of sleep experiments were conducted

Laminar burning velocity is currently one of the metrics for differentiating refrigerant flammability risk per ANSI/ASHRAE Standard 34-2019, Designation and Safety Classification of Refrigerants. Several methods exist for determining laminar burning velocity, and the HVAC&R industry is currently evaluating whether the constant-volume method (CVM) is appropriate for measuring the burning velocity of

Thermal environments generated by diffuse ceiling ventilation (DCV), chilled beam (CB), and chilled ceiling with mixing ventilation (CCMV) systems were compared at different heat loads. Experiments were carried out in two test chambers, in which a double office layout was investigated near heated windows. The heat load strength was increased from a normal level of 37–40 W/floor-m2 to a peak load level

In comparison with constant static pressure and total air volume control strategies, a static pressure reset strategy for variable static pressure control of Variable Air Volume (VAV) air conditioning systems shows evident energy-saving potential. How to establish a relationship between feedback parameters representing the load demand and duct static pressure setpoint has been attached great importance

Air source water chiller (ASWC) (8–90 kW) performance test rooms are expected to be built to manipulate the interior air field only within the prescribed range. The internal air flow field of the test room for ASWC is determined by air supply from the air outlets. In this investigation, the air field of the test room is analyzed in calculation with the air velocities set at 1.5 m/s, 2.0 m/s, 2.5 m/s

The NIST Net-Zero Energy Residential Test Facility (NZERTF) is a highly instrumented, highly configurable, single-family, net-zero energy house occupied by a virtual family of four. A detailed transient model of the NZERTF and the accompanying mechanical equipment was created using information available before construction; the model incorporated building geometric details and construction material

The National Institute of Standards and Technology constructed the Net-Zero Energy (NZE) Residential Test Facility to support the development and adoption of cost-effective NZE designs and technologies. In support of indoor air quality goals, contaminant source control approaches were implemented that minimized the use of products containing urea-formaldehyde resin and utilized products with relatively

This article presents local convective boiling measurements in a micro-fin tube for three low global warming potential refrigerants: R448A, R449A, and R452B. An existing correlation was modified to predict multi-component mixtures, which predicted 98% of the measurements to within ±20%. The new correlation was used to compare the heat transfer coefficient of the three test fluids at the same heat flux

When infectious epidemics occur, they can be perpetuated within health care settings, potentially resulting in severe health care workforce absenteeism, morbidity, mortality, and economic losses. The ventilation system configuration of an airborne infection isolation room is one factor that can play a role in protecting health care workers from infectious patient bioaerosols. Though commonly associated

The climb leg is one of the most acceleration-intensive periods in a passenger aircraft flight. It was previously found that the passenger exposure to cough-released airborne contaminants during a climb may reach 2.8 to 3.0 times that compared to other legs (Elmaghraby et al., Science and Technology for the Built Environment, 2019, accepted. DOI:10.1080/23744731.2019.1576457). In the current study