Airflow Systems Research Articles

Control of Household Refrigerators Part II: Alternate Control Approaches for Improving Temperature Performance and Reducing Energy Use

In Part I it was shown that conventional control of household refrigerators is achieved by regulating the distribution of air in the freezer compartment to all other parts of the plant. In Part II three alternative approaches to the conventional control of a top-mount refrigerator are presented: variable temperature bandwidths, uncoupled compressor and evaporator fan, and the combination of these two. These allowed the plant to achieve near-ideal control with respect to improved temperature performance in each compartment. Automatic airflow dampers were used with the dual controllers to independently regulate refrigerator compartment temperature. Plant performance was simulated using a model that computes the refrigerant and airflow systems behavior. Together, these alternate configurations and approaches define new control algorithms that reveal the plant's optimal control model for improving performance and energy usage relative to conventional controllers. Results based on model simulations are dependent upon the model's accuracy and validity. However, the model validation studies cited here, though limited in scope, do show agreement between simulation and experimental data for the ambient temperatures and thermal load conditions considered. This suggests that these model results are reasonable, and representative of actual plant behavior under these conditions and configurations for a top-mount style refrigerator plant.

The Göteborg Organ Art Center: An international research center for organ history, organ building, teaching, and performance practice

The multidisciplinary Göteborg Organ Art Center (GoArt) project focuses on historical instruments as primary-source documents for performance practice research. Models of instruments are studied to fully document the design and quality of building materials and historical building procedures to explore and reconstruct the aesthetic and practical process of assembly, thereby recovering craft knowledge lost during 20th century industrialization. The project strives to achieve a level of quality in tone-production and craftsmanship not attained since the historical period, providing future organ-builders with functional knowledge of historical craft techniques and the extremely high-quality standards of historical instrument models. Research studies are made in collaboration with the Chalmers University of Technology on antique and contemporary pipe materials, development of new materials with the same properties as the old ones, studies of airflow systems and their effects on tone production in organ pipes, collection and analysis of information about the scaling, dimensions, and design of organ pipes, studies of tone production in organ pipes, and the relationship between organ and room acoustics. This presentation will focus on interaction between organ and church acoustics, studies on subjective perception of organ tone, and flue pipe modeling.

Acoustic analysis and parametric studies of lagged pipes

Pipelines of noisy air or steam flow systems are often lagged on the outside with an acoustically absorptive, highly porous material which in turn is covered with a thin impervious (metallic) jacket. Prediction of transverse insertion loss (reduction in break-out noise) due to this composite lagging is the subject of the present paper. A transfer matrix for the porous absorptive layer is derived for cylindrical waves in the radial direction. Making use of an impedance model, radial velocities of the bare pipe and the outer jacket for the lagged pipe are calculated. These are then combined with respective radiation impedances to calculate insertion loss due to the composite lagging as well as the bare (unconstrained) lagging. Predicted values of insertion loss are compared with the measured values from literature. Finally results of parametric studies are presented.

Industry job descriptions; RN name tags; sterilization of wood; shoe covers; laminar airflow systems

Industry job descriptions; RN name tags; sterilization of wood; shoe covers; laminar airflow systems

Relations between winter precipitation and atmospheric circulation simulated by the geophysical fluid dynamics laboratory general circulation model

AbstractGeneral circulation model (GCM) simulations of atmospheric circulation are more reliable than GCM simulations of temperature and precipitation. Thus, some researchers are developing empirical relations between observed atmospheric circulation and observed temperature and precipitation to translate GCM estimates of future atmospheric circulation into estimates of future regional temperature and precipitation. Developing climate‐change scenarios in this manner assumes, at least, that relationships between atmospheric circulation and surface climate variables, such as temperature and precipitation, are properly simulated by GCMs.In this study, temporal correlations between 700 hPa height anomalies (700 hPa anomalies) over North America simulated by the Geophysical Fluid Dynamics Laboratory (GFDL) GCM and GFDL‐GCM‐simulated (GFDL‐simulated) winter precipitation at eight locations in the conterminous United States are compared with corresponding correlations in observations. The objectives are to (i) characterize the relations between atmospheric circulation and winter precipitation simulated by the GFDL GCM for selected locations in the conterminous USA, (ii) determine whether these relations are similar to those found in observations of the actual climate system, and (iii) determine if GFDL‐simulated precipitation is forced by the same circulation patterns as in the real atmosphere.Results indicate that the GFDL GCM simulates relations between 700 hPa anomalies and local winter precipitation that are similar to relations found in observed data for most of the locations analysed in this study. Results also indicate that at regional scales GFDL GCM simulations of the relations between 700 hPa anomalies and winter precipitation are most similar to observed relations for locations near oceanic sources of atmospheric moisture. These results suggest that the GFDL GCM may not adequately simulate variations in advection of atmospheric moisture into the interior parts of the USA and/or that this moisture is not adequately converted into precipitation in the interior parts of the country. This problem may be due, in part, to (i) the inadequate representation of topography in the GFDL GCM, (ii) stronger‐than‐observed mean winter zonal winds simulated by the GFDL GCM and the consequent more west‐to‐east paths of air flow and storm systems across North America, (iii) the relative weakness of important synoptic patterns in GFDL simulations, such as the Pacific North American circulation pattern, and (iv) the occurrence of ‘spectral rain’.In addition, for some locations, the GFDL‐simulated relationships between precipitation and 700 hPa anomalies can be quite different from observed relations. The differing relationships suggest that GFDL‐simulated changes in regional precipitation in response to changes in atmospheric circulation could differ from changes that would occur in the actual climate system.

Prophylaxis against infection in orthopaedic practice

Prophylaxis against surgical infections is based upon reducing the number of microorganisms which access the wound, and on augmenting normal host defence mechanisms. There is no reason to challenge the importance of the principles of asepsis or of wound excision following injury. The last two decades have seen the growth of prophylaxis using antimicrobial agents and ultra-clean air systems. Although the available data offer less support for their effectiveness than might be supposed from the general acceptance of these measures, it is concluded that use of short-term systemic antibiotic prophylaxis against wound infection is currently justified in open fractures and whenever implants are being inserted. As coagulase negative staphylococci develop increasing resistance to routinely used systemic agents, the use of antibiotic impregnated bone cement appears logical. The case for ultra clean air laminar airflow systems as a cost effective means of reducing infection rates is, despite its plausibility, controversial at the present time.

Cooling Air Flow Systems for a High Heat Density Equipment Room : Part 2-Vertical Distribution Model of Temperature Difference Ratio

Cooling Air Flow Systems for a High Heat Density Equipment Room : Part 2-Vertical Distribution Model of Temperature Difference Ratio

Orographic Effects on Airflow and Mesoscale Weather Systems Over Taiwan

The mountains of Taiwan affect both the airflow and mesoscale weather systems impinging on the island significantly since two-thirds of the landmass of the country is covered by rugged terrain. The orographic feature which has the most significant impact on atmospheric systems is the Central Mountain Range (CMR) which runs through Taiwan in a NNE-SSW direction with a width of about 120 km, a length of about 300 km and an average height of 2 km. The dominant peak of the CMR has a height of 3997 m above the mean sea level. Since Taiwan is surrounded by oceans, it provides a unique environment for studying the orographic effects on prevailing airflow and impinging mesoscale weather systems. In this paper, we review several prominent weather problems related to the orographic effects of the topography of Taiwan, which includes: (a) local rainfall enhancement by the CMR on prevailing winds and mesoscale convective systems, (b) the formation of mesolows and mesocyclones, (c) the effects on Mei-Yu fronts, (d) the effects on mesoscale convective systems, and (e) the influence on typhoon circulations and tracks. Understanding the first four problems is essential in improving the weather forecasting of flash floods in Taiwan during the Mei-Yu season, and is one of the major objectives of the Taiwan Area Mesoscale Experiment (TAMEX) which was a joint field experiment conducted by Taiwanese and American scientists during the period of 1 May to 29 June 1987. When a typhoon impinges on Taiwan, its circulation and track is significantly affected by the CMR. The typhoon track may be continuous or discontinuous depending upon the impinging angle, intensity, and preexisting synoptic scale pressure system. This proposes a serious forecasting problem in Taiwan. Similar problems have also been found in other parts of the world, such as Caribbean islands and Phillipines.

INCREASED SOLAR COLLECTOR'S EFFICIENCY WITH REVERSED-PASS AIR FLOW SYSTEM

The thermal performance of a solar heat collector in which the air path is reversed to flow beneath the absorber plate after passing over it was studied. This type of system is referred to by the authors as the Reversed-Pass Air Flow Collector. Under the same operating conditions (gas flow rate & tilt angle), the rise in air temperature, ΔT, was found to be 10 to 40% higher than that obtained with single-pass air flow (without reversing) system depending upon the prevailing weather conditions. The local heat transfer coefficient from the top surface of the absorber plate was calculated for both types of flow systems and was found to be almost equal. The increased rise in temperature, ΔT, with the reversed-pass air flow system led to an increase in the thermal efficiency of the solar collector. On comparing the two air flow systems, it was noticed that with reversed-pass air flow systems the air is heated at the entrance region, over the absorber's top surface and during the reversed flow from the absorber...

Computer-aided building ventilation system design — a system-theoretic approach

An understanding of the pattern of airflow is an important element in the design of ventilation systems. The airflows are caused by wind effect, stack effect and mechanical ventilation systems. Several models have been developed to analyse the airflow in buildings. So far, the focus has been on the modelling process. In this paper, the modelling and analysis of building ventilation systems using a system-theoretic procedure are presented. The emphasis is on presenting a theoretic derivation of nodal-governing equations for building airflow systems and obtaining efficient procedures for automatic formulation of the system equations. This approach is based on matrix algebra, therefore is easy to implement on a computer.

Laminar Airflow Systems: Issues Surrounding Their Effectiveness

he operating room team must take all possible steps, including structural T improvements in operating room design, to remove extraneous harmful factors during surgery. When changes are as expensive as the wholesale installation of laminar clean airflow systems, however, O R team members must consider if the changes will reduce wound infection rates. The American College of Surgeons Committee on the Operating Room Environment published statements on OR air issues in 1972, 1973, 1976, and 1977.' For the most part, these four statements are as valid today as when they were originally written. In the intervening decade, there have been a number of poorly controlled studies and a few good singleand multi-institutional clinical trials that were done with as much control as possible. When we participated in planning a new hospital and when we prepared program presentations, we reviewed the literature and our own experiences. Even the most recent studies did not

Influence of Smokehouse Air Flow Patterns, Air Changes and Cook Cycles on Texture and Shrinkage of Wieners

ABSTRACTThe effects of two air flow systems, four air changes, and three cook cycles on shrinkage and texture of wieners were investigated. The interaction between air flow patterns and cook cycles was significant for shrinkage revealing the highest weight losses for a low relative humidity cook cycle when combined with the vertical air flow. The interaction of air flow pattern and number of air changes for the texture profile analysis showed significantly higher results for hardness, gumminess, and chewiness when processed at 56 air changes per minute using vertical air flow than for any other combination of treatments. Air changes significantly affected shrinkage and Warner‐Bratzler shear values producing higher values with an increase in the number of air changes.

Nosocomial infection: Prevention by special cleanair, ultraviolet light, and barrier (isolator) techniques

Nosocomial infection: Prevention by special cleanair, ultraviolet light, and barrier (isolator) techniques

Residual Depth Profile in the Evaluation of Granular Adsorbents

The penetration of radioactive CH3131I through adsorbent carbon was studied in air flow systems as a function of bed depth. The count profile in equal increments of depth was found to be exponential with depth along the line of flow for the air-vapor mixtures. The slopes (lognormal count versus depth) were determined for a number of weathered and used carbons as well as for new materials. A large numerical magnitude of the slope is characteristic of new and good carbons; a low value signifies poor retention by the test column. The profile measurements correlate with the percent of penetration. The residual depth profile can serve as an index for the need to replace or to regenerate the carbon bed.

Ultraviolet Irradiation of Air Sterilization under Dynamic Airflow Systems : Bacterial Aerosols Behavior and Inactivation

Ultraviolet Irradiation of Air Sterilization under Dynamic Airflow Systems : Bacterial Aerosols Behavior and Inactivation

Pulse interval and pulse width measurements in determining the flow characteristics in the viewing volume of single particle optical counters

The characteristics of the sample air flow influence some properties of single particle optical counters. The direct measurements of these effects are difficult. In this paper two indirect methods to study these characteristics have been considered. In one method the pulse interval distribution is measured and this is compared with the theoretical distribution. As a result, one can recognize the possible recirculation and the oscillating sample air flow. The other method uses the pulse width distribution to indicate the homogeneity of air flow. The pulse width distribution can also be used to determine the volume of the viewing region. The experimental measurements show that these methods give information about properties and faults of the air flow systems.

Low-Formaldehyde Finishing in Production

The relative importance of the contribution of the various chemical structures present in the fabric to the total formaldehyde-evolution potential of the fabric will vary with the reactant used and finishing conditions. Experience and limited studies with dynamic air-flow systems indicate a correlation between AATCC Test Method 112-1975 results and formaldehyde evolution from the fabric during storage and use. The chemical structure of the reactant nucleus is more important than formalde hyde mole ratios in determining formaldehyde-evolution potential. Methylation of reactants greatly improves their formaldehyde-evolution potential. Proprietary prod ucts can afford even lower formaldehyde-evolution potential. Shifts in equilibria on dilution can increase unreacted formaldehyde in reactants. Nitrate salts or modified magnesium chloride catalysts give good results. Exces sively strong catalysts are detrimental. Relatively high fixation levels are needed to achieve low formaldehyde-evolution potential. Alkalis or buffers have an adverse effect. A near neutral pH on the finished fabric is advantageous.

Computer-aided analysis of airflow systems noise

Computer-aided analysis of airflow systems noise

Energy savings due to changes in design of ventilation and air flow systems

Procedures for the design of ventilation and air flow systems are shown to be energy wasteful. The cause lies both in the methodologies and their technical bases, and in the influence of other factors that enter into a final systems choice for a building (particularly economics). The issue of general outside air requirements is discussed. It is found that any system in which outside air supply is sufficient to control body odor necessarily meets oxygen requirements many times over, and that the ventilation rate can be reduced by about 45% to 60% if higher humidities are used. The long-standing belief that required ventilation flow rate for odor control must increase as air space per occupant decreases has previously been proven untrue, yet a survey of the ASHRAE recommendations and various building codes shows that present standards are based on this inaccurate and energy-wasteful principle. New standards, including a rate of 7.5 cmf/person of outdoor air (not conditioned) during the heating season, are proposed based on the result that the ventilation rate is independent of air space per person. Air distribution systems and sub-systems are analyzed in terms of minimum energy requirements. Energy saving by velocity reduction is discussed. Fan power requirements for a high velocity air distribution system are increased by 2500% over that for a low velocity system in commercial buildings. A comparison of the “old” ASHRAE definition of Effective Temperature, which serves as a thermal comfort criterion in AC systems design, is made with the “new” definition, and the consequent energy savings that should result when the “new” definition is accepted in practice is demonstrated.

Airborne Contamination in Orthopedic Surgery

The question arises whether, on the basis of our studies, the laminar flow system and aspiration suit should be considered as useful and effective components of the overall proctocol to prevent postoperative surgical infections. Our observations do not permit a definitive answer. This would obviously depend on the demonstration of a reduction of the incidence of postoperative infection by means of a large controlled study. The infection rate encountered in this study can not be used to draw any conclusion as to the efficacy of the laminar flow systems, since there are too many uncontrollable variables which may be influential in causing a post operative wound infection. Published reports and present data seem to indicate that the airborne route of transmission is of little significance in modern surgery and that the amount of wound contamination is not necessarily a reflection of airborne contamination. Thus, the use of the laminar air flow system and aspiration suits, which are clearly designed to prevent wound infection by the airborne route, does not seem to be justified on this basis at the present time. On the other hand, the use of laminar air flow system and/or aspiration suit by necessity imposes a strict discipline in those operating rooms, where multiple personnel are routinely involved; i.e., they reduced the number of personnel in contact with patient, reduce the traffic about the surgical patient, etc., which may have significant benefits towards the control of surgical wound infections. This enforced discipline may very well account for the significant decrease in the number of positive intraoperative wound cultures in this study when laminar air flow systems and/or aspiration suits were in use.