HVAC Unit Research Articles

Development of an acoustic design support tool for HVAC ventilation units

HVAC equipment is one of the main sources of noise inside or outside a building. Furthermore, many people are exposed daily to HVAC noise, which can lead to health-related troubles. Therefore, an HVAC mechanical unit must be selected to provide an acceptable sound level transmitted to the occupied spaces of a building and not disturb the community. This paper presents a prediction tool named Sound Prediction Tool (SPT) developed by MJM Acoustical Consultants Inc. in 2021 that allows the engineer (i) to design an HVAC unit with specific mechanical components (filter, coil, etc.) according to his input parameters and (ii) to predict and optimize the sound levels produced by the selected design through its casing and openings (inlet and outlet air). This tool has been validated firstly with acoustical tests ‘’in situ’’ on several separate Air Handling Units (AHU) manufactured by our customer and secondly with Finite Elements Method (FEM) models using Comsol-Multiphysics. Several examples are presented to demonstrate the usefulness of the proposed tool.

Bus Cabin Noise Predictions of Large HVAC System using Total Noise Method

HVAC system design has an accountability towards acoustic comfort of passengers of a vehicle. Owing to larger cabin volume of a bus, multiple air blowers have to be installed to ensure comfort of passengers. Such multiple blowers produce significant flow induced noise inside the cabin. For commercial success, it becomes essential to predict intensity of such a flow induced noise at very early stages in product development. Conventionally sliding mesh based CFD approach is deployed to predict flow and turbulence noise around each blower. However due to complexity, this method becomes computationally intensive resulting in cost and time inefficiency. Hence it is desirable to innovate around an alternative rapid, reliable prediction method, which ensures quick turnaround of prediction. This paper describes a unique innovative approach developed around a multiscale method where flow induced noise generated by a single blower in motion is predicted using commercial Lattice Boltzmann CFD software with a digitally scaled down HVAC system in an anechoic digital wind tunnel. These CFD predictions are used to replace all blowers with virtual stationary speakers inside digital cabin to emulate noise emanated by a large HVAC unit. Authors named this method as total Noise Multiscale Approach, in the paper. With the total multiscale approach, overall sound pressure level predicted inside the bus cabin at rear passenger ear levels are comparable with the physical test measurements and has shown fair correlation. Using this multiscale total noise method, computational cost and turnaround time has significantly reduced compared to the flow conventional resolving approach for cabin with all the blowers. This predictive total noise method found useful in designing and planning countermeasures during product development.

In situ characterisation of exemplary rail vehicle structure borne sound sources

A narrowband characterisation of structure borne sound sources is needed for an accurate prediction of rail vehicle interior noise. Typical rail vehicle sources are relatively large and heavy structures. In 2019, a measurement method for the indirect determination of the blocked force was standardised. It can be applied in situ, with the source connected to an arbitrary receiving structure and was found to be promising for rail vehicle applications in recent research projects. One major challenge is the need to measure the coupled velocity and mobility of all relevant degrees of freedom (six directions per coupling point). Within the European Shift2Rail project DESTINATE, measurements were carried out using a traction motor and an HVAC unit as exemplary sources to investigate the suitability of the in situ method for rail vehicle sources. The measurements include translational and rotational degrees of freedom. Recently, they were further analysed to investigate the effects of neglecting degrees of freedom. The results will be shown in this contribution.

Thermal energy storage to increase the range of electric vehicles under cold conditions

In the last decade, the electric vehicle technology has been establishing and shows a great potential to become predominant in mobility sector. One of the critical problems of current technology is a limited vehicle range compared to extended charging times. Energy consumption of HVAC unit, especially in winter season, can remarkably affect the range. This work evaluates the benefits of introducing a thermal energy storage able to recover the regenerative braking energy excess, in terms of range extension of a light duty commercial vehicle. A detailed digital twin model of the vehicle has been implemented into the Matlab/Simulink platform to this aim. Results show potential benefits up to 10% of increase in vehicle range under winter conditions. Thermal Energy Storage has been then confirming a viable and effective mean to increase the EV range especially under cold ambient conditions.

COMMISIONING AND FAT HVAC FOR OFFSHORE

HVAC stands for Heating Ventilation Air Conditioning, in the industrial world it is very necessary to condition a room according to its needs, it can be used to regulate a room or freeze a product, the selection of HVAC materials for Offshore is very important so that the unit lasts a long time and does not rust easily.
 The importance of selecting materials that are in accordance with the provisions in terms of safety, function and quality, materials that are easy to obtain, sizes according to calculations, aesthetics, and materials that are not easy to rust.
 commissioning is done because to determine the quality and function of the HVAC unit whether it is in accordance with the design, function or calculation.

The Perfect Temperature

A new vertical HVAC unit from Eberspächer impresses with compact design and powerful cooling and heating

Energy Saving to Diminish the Electricity Demand by Regulating HVAC System

Energy saving to diminish the power demand is more important when the substantial increase of electrical tariffs mount financial pressure on monthly budget of the end-users. The higher amount of electricity bill is one of the driving forces to investigate the epicentre of energy consumption at university campus. The objective of the study presented in paper is to test a strategy which could achieve significant reduction in electricity demand and associated bills. The load demand of all buildings and other entities at the campus have analysed using electricity bills of 30 months since 2016 to 2019. From the analysis of collected data, it is observed that HVAC units are responsible for most of electricity consumption at campus. Two split type HVAC units each of 2-ton capacity equipped with rotary compressor have considered in study to measure their energy intakes. Each unit has put in observation for three days with a thermostat setting of 23°C and 25°C. Assuming the similar atmospheric conditions, the HVAC unit at thermostat setting of 25°C has consumed average 147 Watts less power compare to the thermostat setting of 23°C. If the energy saving strategy by regulating set point of thermostat from 23°C to 25°C is deployed to the entire cooling load, it is estimated that hourly 5.33% energy and 0.081 kg of CO2 emission could be saved. This strategy would significantly diminish the electricity bills and support to clean environment. The findings of work are imperative to quantify the significant amount of energy demand reduction at the university campus.

Performance of a Mid-Size Net-Zero Energy Solar House

The University of Alabama at Birmingham (UAB) was one of 16 collegiate teams from around the world that participated in the U.S. Department of Energy Solar Decathlon 2017 competition. An interdisciplinary team of students from across the university was engaged in a 2-year long process to design and build a house that is powered completely by solar power. The house was equipped to run all the typical appliances of an average modern house at similar levels on a conventional power grid. The net-zero house was built and tested on the UAB campus. Considering Birmingham’s weather, a safe room was built to ensure the safety of occupants during events of extreme weather, such as a tornado. A ductless HVAC unit consisting of an inverter-type 3-speed outdoor unit supplied refrigerant to four high-wall indoor units providing the primary source of space conditioning. To achieve a model of efficiency and cost effectiveness, the house incorporated a heavily insulated envelope and precise glazing protection. The roof, floor framing and walls had R-30 batt and foam insulation. With a design informed by southern vernacular language, the building is oriented to maximize solar access and to use roof planes for shading the majority of the year. Peak power generation of the panels was recorded at 9.6 kW. The home has a centralized energy management system that can provide access to energy consumption data and allow control of lighting, appliances, and plug loads remotely. Energy modeling showed that the annual electricity consumption for heating and cooling with variation in wall types were 8470 to 11,661 kWh. For the month of October, it was calculated varying from 683 to 763 kWh, with varying air changes per hour from 0 to 1.5.

Design, dynamic simulation, and optimal size selection of a hybrid solar/wind and battery-based system for off-grid energy supply

Remote energy systems are applicable, especially in critical circumstances like earthquakes, floods, etc. Besides, renewable energy systems are suitable energy sources in remote areas. Therefore, Due to high solar and wind potential and its location as an earthquake-prone, a solar-wind energy system for a remote application on a Conex is presented in this study. Considered wind turbines have power production of 1 kW and 3 kW. PV panels have an efficiency of about 20%. This Conex has 12 m2 of the area and resides three to five people and supplies 520 W power consumption of equipment except for the HVAC unit. A considered lifetime of the Conex is 20 years. The considered capacity of batteries is about 100–200 Ah. Six cities are selected as representatives of the six major climate types in Iran. The studied system is optimized for each city. The heating and cooling demand of Conex in cities are specified using TRNSYS software. The heat pump's electricity requirement as a cooling and heating unit with COP of four, lighting (20 W), laptops (140 W), and refrigerators (360 W) is calculated for Conex in each city. Mixed-integer linear programming is employed to optimize an off-grid renewable energy system to supply this electricity demand. The system's total cost, which includes the initial and O&M cost of PV panels and wind turbines, and the capital and replacement cost of the batteries together with the loss of power supply probability during a year, are considered two objective functions. The interest rate is assumed to be 15%. Achieved results show that Iran's solar and wind potential can balance the required load of the Conex with a probability of power outage as low as 1% of a year. However, there is a variance in the cost of the required renewable energy system for supplying Conex power consumption for different climate zones: in the Mediterranean region, the system costs 500–5000 $ as the most expensive one, and in the hot coastal dry region, it costs 900 $-2000 $ as the most cost-efficient region. Finally, results show that wind turbines can be cost-effective energy suppliers for most considered climates, especially considering O&M costs. This study can fill the gap of requiring off-grid temporary portable residences in different climates after disasters, which destroy buildings. Therefore, the lack of these temporary residences can be supplied without adding greenhouse gases to the environment, which reduces greenhouse emissions and electrical grid dependence of the building sector.

Parametric investigation of a\xa0chilled water district cooling unit using mono and hybrid nanofluids

This study presents a novel parametric investigation into the performance of a district cooling system using mono (Al2O3 and TiO2) and hybrid (Al2O3–TiO2) nanoparticles in the base fluids of water and ethylene–glycol water (EG-water) at a 20:80 ratio. The study analyses the effect of variables such as secondary fluid flow rate, evaporator and inlet temperatures, nanoparticle concentration, and air flowrate on the COP, total electrical energy consumption, and design of the district cooling unit. The analysis is performed with a thermal model developed and validated using operations data obtained from the McQuay chilled water HVAC unit operating in one of the facility plants at the Education City campus. The results of the study show that the use of nanofluids increased the overall heat transfer coefficient in the system by 6.6% when using Al2O3–TiO2/water nanofluids. The use of nanofluids in the evaporator also led to an average reduction of 23.3% in the total work input to the system and improved the COP of the system by 21.8%, 20.8% and 21.6% for Al2O3–TiO2/water, Al2O3/water, and TiO2/water nanofluids, respectively. Finally, an enhancement of 21.6% in COP was recorded for Al2O3–TiO2/EG-water nanofluids at a 5% nanoparticle volume concentration.

860. A Proposed Standard for Hospital Bioaerosol Monitoring in Avoiding Nosocomial Mould Infections

BackgroundRecent nosocomial outbreaks of mould infections have been linked to bioaerosols. Active and passive environmental sampling is a primary method of quantifying airborne contamination in the hospital, but currently there are no standardized Occupational Exposure Limits (OELs) for the avoidance of nosocomial infections.MethodsBetween March 2016 and December 2019, 186 post-construction/post-cleaning air samples were collected to measure particle counts based on defined size criteria Lighthouse handheld Particle Counter) and viable air fungal cultures (Anderson single stage N6 Viable Particulate Sampler) across wards of a 1,082 bed hospital in Houston, Texas, and compared with outdoor controls. Areas were cleared for occupancy if the ≤ 0.3micron particle counts were reduced by the expected efficacy of the HVAC unit and if indoor fungi airborne concentrations in CFU/m³ were also reduced or did not exceed the outdoor ambient reference levels for each separate day of site assessment.ResultsThe mean counts of particles ≤ 0.3microns were as follows: floors 37,427.50 (-32% reduction), operating rooms 8,163.88 (95% reduction), OR sterile core 15,001.31 (89% reduction), ICU 7,640.15 (93% reduction), radiology suites 1,046.25 (97% reduction), and outpatient areas 17,891.58 (82% reduction). The table indicates the reported mean density (CFU/m³) data and species of fungi isolated in viable bioaerosol samples, 13 of which matched outdoor reference isolates. The mean density of outdoor cultures was 292.37 compared to all indoor units 24.53 (91.61% reduction), floors 25.44 (91.3% reduction), ICUs 28.19 (90.4% reduction), radiology suites 22.5 (92.3% reduction), and ORs 12.79 (95.6% reduction). During this time, no nosocomial fungal infections or outbreaks were documented for the institution.Table 1: Mean Density (cfu/mm3) of Fungal Species per Location ConclusionAn indoor air quality standard comprised of particle count data reduced by the expected efficacy of the operating HVAC unit and also existing indoor viable fungi in units of CFU/m³ that did not exceed the outdoor reference could potentially be correlated with avoidance of nosocomial mould infections.Disclosures Luis Ostrosky-Zeichner, MD, Amplyx (Scientific Research Study Investigator)Astellas (Consultant, Scientific Research Study Investigator, Other Financial or Material Support, Non-branded educational speaking)Biotoscana (Consultant, Other Financial or Material Support, Non-branded educational speaking)Cidara (Consultant, Scientific Research Study Investigator)F2G (Consultant)Gilead (Consultant)Mayne (Consultant)Octapharma (Consultant)Pfizer (Other Financial or Material Support, Non-branded educational speaking)Scynexis (Consultant, Grant/Research Support, Scientific Research Study Investigator)Stendhal (Consultant)Viracor (Consultant)

Windshield Defrost Simplified CFD Model

Abstract The windshield defrost system, in general, is a vehicle safety feature. Thus, its restricted by variety of directives. However, the OMEs’ benchmark targets could be even more demanding as the deicing process is in addition also part of passengers comfort. From vehicle design point of view the wind-shield defrost system is typically connected to HVAC unit (Heating, Ventilation and Air Conditioning). In the technical solution the windshield is heated via hot air convection. Nevertheless, other methods are becoming more and more popular, like directly heated glass by hot wire ohmic heating (heated glasses). The defrost CFD model should predict the ice layer thickness in time and space and in environmental conditions defined according to appropriate directives and technical solution. The accurate and fast modelling technique is essential part of a vehicle development, especially nowadays, where the optimization techniques area widely used and requires hundreds of simulations runs. Modelling requests are even increasing with modern pure electric vehicles (EVs), were the thermal and energy management is more demanding compared to the classical internal combustion engine (ICE) vehicles. The aim of the work is to verify possibility to model the ice layer thickness with simplified approach, which could be beneficial from computational time burden.

Analysing the effects of thermal comfort and indoor air quality in design studios and classrooms on student performance

This study aimed to explore the various effects of different ventilation modes on the thermal comfort and indoor air quality in design education environment. It also investigated the relationship between the ventilation mode and student performance. Thus, an experimental study was conducted in both studio and classroom environments, in Interior Architecture and Environmental Design Department at Bilkent University, Ankara, Turkey. CO2 concentration values, indoor air temperature and humidity values as the main parameters of thermal comfort and indoor air quality was measured in both winter and summer seasons under the three modes of ventilation: 1) without opening door and windows mode setting; (2) natural ventilation mode and (3) the HVAC ventilation mode achieved by the TROX school-air unit. Under these three different modes for both attention and concentration levels, 100 students from the winter season, 50 students from summer season for the classroom environment, and 20 students from the winter season, 16 students from summer season for the studio environment participated. Results were calculated in IBM SPSS 21 software separately for both seasons and three different ventilation modes. As a result, the experimental and performance results have shown that the HVAC unit mode achieved the most satisfactory indoor environment in both seasons and higher levels of student performance.

PrivHome: Privacy-Preserving Authenticated Communication in Smart Home Environment

A smart home enables users to access devices such as lighting, HVAC, temperature sensors, and surveillance camera. It provides a more convenient and safe living environment for users. Security and privacy, however, is a key concern since information collected from these devices are normally communicated to the user through an open network (i.e. Internet) or system provided by the service provider. The service provider may store and have access to these information. Emerging smart home hubs such as Samsung SmartThings and Google Home are also capable of collecting and storing these information. Leakage and unauthorized access to the information can have serious consequences. For example, the mere timing of switching on/off of an HVAC unit may reveal the presence or absence of the home owner. Similarly, leakage or tampering of critical medical information collected from wearable body sensors can have serious consequences. Encrypting these information will address the issues, but it also reduces utility since queries is no longer straightforward. Therefore, we propose a privacy-preserving scheme, $\sf {PrivHome}$ PrivHome . It supports authentication, secure data storage and query for smart home systems. $\sf {PrivHome}$ PrivHome provides data confidentiality as well as entity and data authentication to prevent an outsider from learning or modifying the data communicated between the devices, service provider, gateway, and the user. It further provides privacy-preserving queries in such a way that the service provider, and the gateway does not learn content of the data. To the best of our knowledge, privacy-preserving queries for smart home systems has not been considered before. Under our scheme is a new, lightweight entity and key-exchange protocol, and an efficient searchable encryption protocol. Our scheme is practical as both protocols are based solely on symmetric cryptographic techniques. We demonstrate efficiency and effectiveness of our scheme based on experimental and simulation results, as well as comparisons to existing smart home security protocols.

Experimental investigation on energy saving potential of smart HVAC unit

ABSTRACTIt is well known that ‘the energy can’t be created but could be saved’ and the energy resources are depleting at an alarming rate over the decades. The HVAC unit consumes 1/5th of the World’s electrical power consumption. Over the years several modifications have been made on the HVAC unit to save energy. This study implements the machine-to-machine interaction through Internet of things which reduces the human effort. The proposed system utilises the smart power controlling and modifying feedback systems from mobile phones integrated with human motion detectors. Due to the accurate feedback system, the room temperature can be maintained within the range of ±0.3°C. The experiment shows an interesting result that the power consumption of compressor can be reduced by 45% using the smart control HVAC unit. The client can also control the system through a web server which controls the actuators.

Dynamic performance assessment of a solar-assisted desiccant-based air handling unit in two Italian cities

Desiccant-based air handling units can provide significant operational advantages and can use solar energy as the main heat source. Hereinafter a plant equipped with a silica-gel desiccant wheel is analyzed for two Italian locations (Benevento and Milano).A parametric study involving collectors types, surfaces, tilt angles and installation site has been performed. The proposed system has been compared with a conventional HVAC unit, through dynamic simulations. In terms of energy and environmental analysis, solar desiccant systems should always be preferred to conventional ones, even when the solar thermal energy surplus is fully dissipated. A maximum primary energy saving of about 10% and 20% with flat plat and evacuated tube collectors, respectively, occurs in both locations. The savings increase up to about 58% and 72% in Benevento and 43% and 58% in Milano, when the solar heat excess is completely used for further energy demands.One observes that systems with evacuated tube collectors are preferable where the available space for the solar field is small, instead with larger surfaces flat plate collectors are advantaged.In terms of economic analysis, the shortest payback periods are 6 and 8years for Benevento and Milano, respectively.

Airflow Measurement of the Car HVAC Unit Using Hot-wire Anemometry

Thermal environment in a vehicular cabin significantly influence drivers’ fatigue and passengers’ thermal comfort. This environment is traditionally managed by HVAC cabin system that distributes air and modifies its properties. In order to simulate cabin thermal behaviour, amount of the air led through car vents must be determined. The aim of this study was to develop methodology to measure airflow from the vents, and consequently calculate corresponding air distribution coefficients. Three climatic cases were selected to match European winter, summer, and spring / fall conditions. Experiments were conducted on a test vehicle in a climatic chamber. The car HVAC system was set to automatic control mode, and the measurements were executed after the system stabilisation—each case was independently measured three times. To be able to evaluate precision of the method, the airflow was determined at the system inlet (HVAC suction) and outlet (each vent), and the total airflow values were compared. The airflow was calculated by determining a mean value of the air velocity multiplied by an area of inlet / outlet cross-section. Hot-wire anemometry was involved to measure the air velocity. Regarding the summer case, total airflow entering the cabin was around 57 l s -1 with 60 % of the air entering the cabin through dashboard vents; no air was supplied to the feet compartment. The remaining cases had the same total airflow of around 42 l s -1 , and the air distribution was focused mainly on feet and windows. The inlet and outlet airflow values show a good match with a maximum mass differential of 8.3 %.

Implementation of model predictive control for an HVAC system in a mid-size commercial building

The article presents field experiment results from the implementation of a model predictive controller which optimizes the operation of a variable volume, dual-duct, multi-zone HVAC unit serving an existing mid-size commercial building. This full-scale proof-of-concept study was used to estimate the benefits of implementing advanced building control technologies during a retrofit. The control approach uses dynamic estimates and predictions of zone loads and temperatures, outdoor weather conditions, and HVAC system models to minimize energy consumption while meeting equipment and thermal comfort constraints. The article describes the on-line implementation of the hierarchical control system, including communication of the optimal control scheme with the building automation system, the controlled set-points and the component-level feedback loops, as well as the measured energy and indoor comfort performance benefits from the demonstration. The building-scale experiments and the receding-horizon control algorithm implementation results are described. Site measurements show this algorithm, when implemented in state-of-the-art direct digital control systems, consistently yields energy savings and reduces peak power while improving the indoor thermal comfort. The demonstration results show energy savings of 20% on average during the transition season, 70% on average during heating season, and 10% or more peak power reduction, all relative to pre-configured, rule-based schedules implemented in the retrofitted direct digital control system.

Performance Study of Hydrocarbon Mixture for Green Vehicle Air-conditioning System

Experimental tests were conducted to monitor vehicle air-conditioning system in real life using hydrofluorocarbons (HFC-R134a) and hydrocarbon refrigerant as the working fluid for the compressor. The major variable for this study is vehicle speed. The tests were conducted on a roller dynamometer using a 5 door A-segment hatchback vehicle with a 1.3liter petrol engine to stimulate an actual vehicle on a level road with HVAC unit operating at a temperature set point of 21°C and blower speed at 2. The weight and internal heat load from passengers are taken into considerations with ambient temperature of 30°C and humidity of surrounding conditions at 50-65%. The result shows positive improvements on temperature distribution and fuel conservation with a possibility to be as an alternative refrigerant without any necessity of changing parts in the current system.

Bus HVAC energy consumption test method based on HVAC unit behavior

This paper presents a test method for determination of energy consumption of bus HVAC unit. The energy consumption corresponds to a bus engine fuel consumption increase during the HVAC unit operation period. The HVAC unit energy consumption is determined from the unit input power, which is measured under several levels of bus engine speeds and at different levels of testing heat load in the laboratory environment. Since the bus engine fuel consumption is incrementally induced by powering an HVAC unit, the results are subsequently recalculated to the unit fuel consumption under the defined road cycles in terms of standardized diesel engine. The method is likewise applicable either for classic or electric HVAC units with a main consumer (compressor or high voltage alternator) mechanically driven directly from the bus engine and also for electric HVAC units supplied from an alternative electric energy source in case of hybrid or fully electric buses.