Heating, Ventilation, And Air Conditioning Duct Research Articles

빌딩 내 공조 닥트의 무선망 활용을 위한 전파 특성 측정

본 논문에서는 빌딩 내부의 공조 닥트를 이용한 무선 통신망의 전파 특성을 측정하고 분석한다. 공조 피더 구조를 분석하고 전송 모드를 여기할 수 있는 피더 장치를 제작하여 시뮬레이션을 통하여 여기 특성을 분석한다. 2.45 GHz 와이파이 대역에서 실제 건물 내부의 공조 닥트를 통해 송수신되는 전파의 세기를 측정하고, LOS 환경 및 격벽이 있는 사무실 그리고 복도 등 여러 실내 환경 조건에서 전파를 측정하여 닥트 피더 방식과 비교한다. 측정 및 분석 결과를 활용하여 닥트를 이용한 무선망 설계 방법을 제안한다. In this paper, we measure and analyze propagation characteristic of heating, ventilation, and air conditioning(HVAC) ducts within buildings for wireless networks. We analyze the duct structures, implement the feeders exciting propagating modes, and simulate the excitation characteristic. We measure the propagation characteristic of HAVC ducts at 2.45 GHz WiFi band and compare it with that of LOS and partitioned office environments. We propose the design method of wireless network using HVAC ducts based on our results.

Vortex shedding induced energy harvesting from piezoelectric materials in heating, ventilation and air conditioning flows

A cantilevered piezoelectric beam is excited in a heating, ventilation and air conditioning (HVAC) flow. This excitation is amplified by the interactions between (a) an aerodynamic fin attached at the end of the piezoelectric cantilever and (b) the vortex shedding downstream from a bluff body placed in the air flow ahead of the fin/cantilever assembly. The positioning of small weights along the fin enables tuning of the energy harvester to operate at resonance for flow velocities from 2 to 5 m s−1, which are characteristic of HVAC ducts. In a 15 cm diameter air duct, power generation of 200 μW for a flow speed of 2.5 m s−1 and power generation of 3 mW for a flow speed of 5 m s−1 was achieved. These power outputs are sufficient to power a wireless sensor node for HVAC monitoring systems or other sensors for smart building technology.

Predicting insertion loss of large duct systems above the plane wave cutoff frequency

If the dimensions of a silencer or muffler component are small compared to an acoustic wavelength, plane wave propagation can be assumed. This is not the case for HVAC (heating, ventilation, and air conditioning) duct systems, and large diesel engine mufflers commonly used in ship and generator sets. For such applications, the wave behavior in the inlet and outlet ducts is three-dimensional. In this paper, the finite element method is utilized to simulate large duct systems with an aim to predict the insertion loss. The boundary condition on the source side is a diffuse field applied by determining a suitable cross-spectral force matrix of the excitation. At the termination, the radiation impedance is calculated utilizing a wavelet algorithm. Simulation results are compared to published measurement results for HVAC plenums and demonstrate good agreement.

Long Range Passive UHF RFID System Using HVAC Ducts

In this paper, the use of hollow metal heating, ventilating, and air-conditioning (HVAC) ducts as a potential communication channel between passive ultrahigh-frequency (UHF) radio-frequency identification (RFID) readers and tags is studied. HVAC ducts behave as electromagnetic waveguides with much lower signal attenuation compared to free-space propagation. This low-loss electromagnetic environment allows one to greatly increase the communication range of passive UHF RFID systems and build, for example, a long range passive sensor network spanning an entire infrastructure such as a large building. In this work, it is shown both theoretically and experimentally that the read range of passive UHF RFID systems can be increased by multiple times compared to operation in a free-space environment.

Modeling deposition of particles in vertical square ventilation duct flows

The presence, flow, and distribution of particle in heating, ventilation, and air-conditioning (HVAC) ducts influence the quality of air in buildings and hence the health of building occupants. To shed a better light on the flow of particles in HVAC ducts this a paper has considered the effects of drag, lift force, gravity, Brownian diffusion, and turbulent diffusion on the dimensionless deposition velocity of particles in smooth vertical ventilation ducts using fully developed and developing velocity profiles. Based on the Reynolds stress transport model (RSM) at two different air velocities, 3.0 m/s and 7.0 m/s, the aforementioned effects were predicted using Reynolds-averaged Navier–Stokes (RANS)–Lagrangian simulation on square shaped ducts under vertical flows. Preliminary results suggest that the gravity of particles does not directly change the dimensionless deposition velocity in vertical flows. Nevertheless, the gravity of particles contributes to changing the Saffman lift force. It is thus the Saffman lift force that directly changes the dimensionless deposition velocity of particles in vertical flows. In addition, the difference in the dimensionless deposition velocities between fully developed and developing flows is owing to the turbulent diffusion, turbulent intensity, and needless to say, the Saffman lift force under different dimensionless particle relaxation time.

Aero‐acoustic predictions of automotive dashboard HVAC (heating, ventilating, and air‐conditioning ducts).

The flow‐induced noise generated by automotive climate control systems is today emerging as one of the main noise sources in a vehicle interior. Numerical simulation offers a good way to analyze these mechanisms and to identify the aerodynamic noise sources in an industrial context driven by permanent reduction in programs timing and development costs, implying no physical prototype of ducts before serial tooling. This paper focuses on a numerical aeroacoustic study of automotive instrument panel ducts to estimate the sound produced by the turbulent flow. The methodology is the following: the unsteady‐flow field is first computed using a CFD solver—here FLUENT. Then, the acoustic finite element solver ACTRAN computes the acoustic sound sources from these time domain CFD results. The sources are finally propagated into the vehicle interior in the frequency domain. One advantage of the technique is that the CFD computations are completely separated from the acoustic computations. This allows reusing one CFD computation for many different acoustic computations. The theoretical background is presented in the first sections of this paper. Then, the accuracy of the method for real industrial cases is demonstrated by comparing the numerical results to experimental results available at VISTEON.

Prediction of Breakout Noise from Acoustically Lagged Rectangular HVAC Ducts

Heating, ventilation and air-conditioning (HVAC) ducts are often lagged on the outside of the duct wall with a highly porous material, covered in turn with a thin impervious jacket. This arrangement is used to provide thermal insulation as well as the breakout noise reduction. In this paper, a prediction method based on the four-pole parameters is discussed to evaluate the lagged duct performance in terms of the breakout noise reduction in the plane-wave frequency range. Transfer matrix of the inner and outer duct walls in the transverse direction is calculated using the wall admittance as a function of the axial wave number. Assuming a common axial wave number ensures coupling between the acoustic waves and structural waves. It is a function of the wall admittance. Considerable difference between common axial wave number and the air acoustic wave number is observed near the coupling frequency region of the duct wall. The overall transfer matrix is developed in order to relate the inside plane wave pressure to the outer acoustic particle velocity. This is combined with the radiation impedance of the duct to predict the transverse transmission loss. Net Insertion loss of the lagged duct is calculated using the difference of the transverse transmission loss of the lagged duct and the corresponding bare duct. Predicted values of the insertion loss are compared with the measured values from literature. Finally, results of parametric studies are presented.

Particle loading rates for HVAC filters, heat exchangers, and ducts

The rate at which airborne particulate matter deposits onto heating, ventilation, and air-conditioning (HVAC) components is important from both indoor air quality (IAQ) and energy perspectives. This modeling study predicts size-resolved particle mass loading rates for residential and commercial filters, heat exchangers (i.e. coils), and supply and return ducts. A parametric analysis evaluated the impact of different outdoor particle distributions, indoor emission sources, HVAC airflows, filtration efficiencies, coils, and duct system complexities. The median predicted residential and commercial loading rates were 2.97 and 130 g/m(2) month for the filter loading rates, 0.756 and 4.35 g/m(2) month for the coil loading rates, 0.0051 and 1.00 g/month for the supply duct loading rates, and 0.262 g/month for the commercial return duct loading rates. Loading rates are more dependent on outdoor particle distributions, indoor sources, HVAC operation strategy, and filtration than other considered parameters. The results presented herein, once validated, can be used to estimate filter changing and coil cleaning schedules, energy implications of filter and coil loading, and IAQ impacts associated with deposited particles. The results in this paper suggest important factors that lead to particle deposition on HVAC components in residential and commercial buildings. This knowledge informs the development and comparison of control strategies to limit particle deposition. The predicted mass loading rates allow for the assessment of pressure drop and indoor air quality consequences that result from particle mass loading onto HVAC system components.

On the Capacity Limits of HVAC Duct Channel for High-Speed Internet Access

In this paper, we report theoretical and experimental channel-capacity estimates of heating, ventilation, and air conditioning (HVAC) ducts based on multicarrier transmission that uses M-ary quadrature amplitude modulation and measured channel responses at the 2.4-GHz industrial, scientific, and medical band. It is shown theoretically that data rates in excess of 1 Gb/s are possible over distances up to 500 m in straight ducts in which reflections have been suppressed. Our experimental results also show that even in the case of more complex HVAC duct networks (i.e., HVAC duct networks that include bends, tees, etc.) data rates over 2 Gb/s are possible. Our estimations in this case are valid for distances of up to 22 m, which was the maximum distance of our experimental setup. These experimental results, measured with a large-scale testbed set up at Carnegie Mellon University, Pittsburgh, PA, albeit limited in terms of transmitter-receiver separation distance, provide further evidence on the potential of HVAC systems as an attractive solution for providing communications in indoor wireless networks.

A Simple Path-Loss Prediction Model for HVAC Systems

In this paper, we present a simple path-loss prediction model for link budget analysis in indoor wireless local area networks that use heating, ventilation, and air conditioning (HVAC) cylindrical ducts in the 2.4-2.5-GHz industrial, scientific, and medical band. The model we propose predicts the average power loss between a transmitter-receiver pair in an HVAC duct network. This prediction model greatly simplifies the link budget analysis for a complex duct network, making it a convenient and simple tool for system design. The accuracy of our prediction model is verified by an extensive set of experimental measurements.

A novel mode content analysis technique for antennas in multimode waveguides

This paper presents a novel technique for analyzing the mode content excited by antennas placed in multimode waveguides. The technique is based on measuring the frequency response between the two antennas coupled into a waveguide and using that information to extract the mode content generated by the transmitting antenna. The technique is applicable to cases in which the mode amplitudes are approximately constant over the frequency range of interest. This method is valuable for determining the mode mix generated by arbitrary transmitting antennas in a multimode waveguide propagation environment. An example of such an environment is heating, ventilation, and air-conditioning (HVAC) ducts used for indoor communications, where an important antenna characteristic is the mode sensitivity (analogous to the antenna directive gain in free space). We validate our technique with the example of a monopole probe antenna coupled into a multimode cylindrical HVAC duct.

Impulse Response of the HVAC Duct as a Communication Channel

Heating, ventilation, and air conditioning (HVAC) ducts in buildings behave as multimode waveguides when excited at radio frequencies and thus, can be used to distribute radio signals. The channel properties of the ducts are different from the properties of a usual indoor propagation channel. In this paper, we describe physical mechanisms which affect the HVAC channel impulse response and analyze their influence on the delay spread. Those mechanisms include antenna coupling, attenuation, and three types of dispersion: intramodal, intermodal, and multipath. We analyze each type separately and explore the behavior of the delay spread as a function of distance in straight ducts. Experimental channel measurements taken on real ducts confirm the validity of our model.

Propagation model for the HVAC duct as a communication channel

Heating, ventilation, and air conditioning (HVAC) ducts in buildings are typically hollow metal pipes which can be used as waveguides to carry signals and provide network access to offices. Knowledge of channel properties is crucial to designing such a communication system. The paper presents a propagation model for a straight HVAC duct terminated at both ends. At high frequencies, this duct behaves as a multimode waveguide with a transmitting antenna coupling in and a receiving antenna coupling out. We derive a simple analytical expression for the frequency response of this channel using conventional techniques. Experimental data taken on real circular ducts excited by monopole probe antennas confirm the theoretical results. This model represents an initial step toward the development of a tool for planning a wireless distribution system using building HVAC ducts.

Evaluation of Fungal Growth on Fiberglass Duct Materials for Various Moisture, Soil, Use, and Temperature Conditions

Abstract Fiberglass duct materials are commonly used in both residential and commercial heating, ventilation, and air-conditioning (HVAC) systems to provide the needed thermal insulation and noise control. Many building investigations have documented biocontamination of these materials, and the appropriateness of their use in high humidity locations has come into question. A series of experiments, each lasting 6 weeks, was conducted in static environmental chambers to assess some of the conditions that may impact the ability of a variety of fiberglass materials to support the growth of a fungus, Penicillium chrysogenum. Three different fiberglass duct liners (FDL), one fiberglass duct board, and fiberglass insulation, all newly purchased, were obtained as were samples of used (>5 years old) materials. Samples of these materials were tested to evaluate the effects of moisture, soil, use, and temperature on their ability to support the growth of P. chrysogenum. These studies demonstrated that P. chrysogenum could amplify under conditions of low (12°C) and room (23°C) temperature and high relative humidity on samples of one of the newly purchased materials, and that either wetting and/or soiling increased the materials’ susceptibility. P. chrysogenum was able to grow on all the used material samples. While the results of this study apply directly only to fiberglass duct materials, they suggest that dust accumulation and/or high humidity should be properly controlled in any HVAC duct to prevent the growth of P. chrysogenum.

Computer-generated flat-pattern development of heating, ventilating and air-conditioning ductings

The production of heating, ventilating and air-conditioning (HVAC) ducts is a common production activity in the sheet metal industry. When part of the duct involves transition elements, the development of the transitional surface to form the flat pattern is often accomplished laboriously by manual drafting techniques. In this paper, algorithms are described that can be used for automatically generating these flat patterns for several classes of HVAC ducts. The algorithms have been implemented on a PC through interfacing a family of c-programs with the Autocad drafting and design system. The c-programs perform the numerical calculations rapidly while Autocad is used mainly for the user interface and for displaying the flat patterns. Cardboard models were constructed from the drawings of the generated flat patterns to verify the correctness of the algorithms.

Computer-generated flat-pattern development of heating, ventilating and air-conditioning ductings

The production of heating, ventilating and air-conditioning (HVAC) ducts is a common production activity in the sheet metal industry. When part of the duct involves transition elements, the development of the transitional surface to form the flat pattern is often accomplished laboriously by manual drafting techniques. In this paper, algorithms are described that can be used for automatically generating these flat patterns for several classes of HVAC ducts. The algorithms have been implemented on a PC through interfacing a family of c-programs with the Auto cad drafting and design system. The c-programs perform the numerical calculations rapidly while Auto cad is used mainly for the user interface and for displaying the flat patterns. Cardboard models were constructed from the drawings of the generated flat patterns to verify the correctness of the algorithms.