Fungal colonization of air filters for use in heating, ventilating, and air conditioning (HVAC) systems

1995 ◽  
Vol 14 (1) ◽  
pp. 41-45 ◽  
Author(s):  
R. B. Simmons ◽  
S. A. Crow
Keyword(s):  
Air Conditioning ◽  
Hvac Systems ◽  
Fungal Colonization ◽  
Air Filters

scholarly journals A Multi-Timescale Bilinear Model for Optimization and Control of HVAC Systems with Consistency

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 400 ◽  
Author(s):  
Zelin Nie ◽  
Feng Gao ◽  
Chao-Bo Yan
Keyword(s):  
Optimization Model ◽  
Air Conditioning ◽  
State Of The Art ◽  
Hvac Systems ◽  
Practical Significance ◽  
Hvac System ◽  
Bilinear Model ◽  
Optimization And Control ◽  
And Control ◽  
Slow Timescale

Reducing the energy consumption of the heating, ventilation, and air conditioning (HVAC) systems while ensuring users’ comfort is of both academic and practical significance. However, the-state-of-the-art of the optimization model of the HVAC system is that either the thermal dynamic model is simplified as a linear model, or the optimization model of the HVAC system is single-timescale, which leads to heavy computation burden. To balance the practicality and the overhead of computation, in this paper, a multi-timescale bilinear model of HVAC systems is proposed. To guarantee the consistency of models in different timescales, the fast timescale model is built first with a bilinear form, and then the slow timescale model is induced from the fast one, specifically, with a bilinear-like form. After a simplified replacement made for the bilinear-like part, this problem can be solved by a convexification method. Extensive numerical experiments have been conducted to validate the effectiveness of this model.

scholarly journals Some Aspects of HVAC Design in Energy Renovation of Buildings

2021 ◽  
Author(s):  
Taghi Karimipanah
Keyword(s):  
Renewable Energy ◽  
Air Conditioning ◽  
Distribution Systems ◽  
Energy System ◽  
Building Energy ◽  
Hvac Systems ◽  
Heat Losses ◽  
Energy Sources ◽  
Air Distribution ◽  
Building Energy System

It is well-known fact that air conditioning systems are responsible for a significant part of all energy systems in building energy usage. In EU buildings, the building HVAC systems account for ca 50% of the energy consumed. In the U.S., air-conditioning accounts on average about 12% of residential energy expenditures. The proper choice of air distribution systems and sustainable energy sources to drive the electrical components have a vital impact to achieve the best requirements for indoor climate including, hygienical, thermal, and reasonable energy-saving goals. The building energy system components that have a considerable impact on the demand for final energy in the building are design, outdoor environment conditions, HVAC systems, water consumption, electrical appliances, indoor thermal comfort, and indoor human activities. For calculation of the energy balance in a building, we need to consider the total energy flows in and out from the building including ventilation heat losses, the perimeters transmission heat loses, solar radiation, internal heat from occupants and appliances, space and domestic water heating, air leakage, and sewage heat losses. However, it is a difficult task to handle the above time-dependent parameters therefore an energy simulation program will always be used. This chapter aims to assess the role of ventilation and air-conditioning of buildings through the sustainability approaches and some of the existing renewable energy-based methods of HVAC systems are presented. This comprehensive review has been shown that using the new air distribution systems in combination with renewable energy sources are key factors to improve the HVAC performance and move toward Nearly Zero Carbon Buildings (NZCB).

scholarly journals Dynamic simulation of indirect air conditioning systems with optimized computational time

2019 ◽  
Vol 111 ◽  
pp. 04042
Author(s):  
Nicolás Ablanque ◽  
Santiago Torras ◽  
Carles Oliet ◽  
Joaquim Rigola ◽  
Carlos-David Pérez-Segarra
Keyword(s):  
Air Conditioning ◽  
Energy Savings ◽  
Control Strategies ◽  
Model Potential ◽  
Hvac Systems ◽  
Object Oriented Programming ◽  
Computational Time ◽  
Air Conditioning System ◽  
Numerical Resolution ◽  
Air Conditioning Systems

The simulation of HVAC systems is a powerful tool to improve the energy efficiency in buildings. The modelling of such systems faces several obstacles due to both the physical phenomenology present and the numerical resolution difficulties. The present work is an attempt to develop a robust, fast, and accurate model for HVAC systems that can interact with the other relevant systems involved in buildings thermal management. The whole system model has been developed in the form of libraries under the Modelica language to exploit its advantageous characteristics: object-oriented programming, equationbased modelling, and handling of multi-physics. The global resolution is carried out dynamically so that not only steady-state predictions can be conducted but also control strategies can be studied over meaningful periods of time. This latter aspect is crucial for optimizing energy savings. The libraries include models for all the system individual components such as pumps, compressors or heat exchangers (operating with twophase flows and/or moist air) and also models assemblies to account for vapour compression units and liquid circuits. An illustrative example of an indirect air conditioning system is detailed in the present work in order to highlight the model potential.

Failure of the Sterile Air-Flow Component of a Protected Environment Detected by Demonstration of Chaetomium Species Colonization of Four Consecutive Immunosuppressed Occupants

1988 ◽  
Vol 9 (10) ◽  
pp. 451-456 ◽  
Author(s):  
Gail L. Woods ◽  
J. Calvin Davis ◽  
William P. Vaughan
Keyword(s):  
High Efficiency ◽  
Marrow Transplant ◽  
Fungal Colonization ◽  
Transplant Recipients ◽  
Special Care Unit ◽  
Air Filters ◽  
X Ray ◽  
Increased Risk ◽  
Chest X Ray ◽  
Protective Environment

AbstractFour bone marrow transplant recipients consecutively occupying the same room on our Oncology-Hematology Special Care Unit (OHSCU) became colonized with Chaetomium species between January and April, 1987. These patients, aged 27 to 43 years, were immunocompromised as a result of intensive chemotherapy, and were consequently at increased risk for development of invasive fungal infection. At the time of Chaetomium colonization, all patients were febrile, two had transient new infiltrates on chest x-ray, and three were receiving amphotericin B therapy. Subsequent environmental cultures revealed Chaetomium contamination of the OHSCU air-handling system, including the HEPA (high-efficiency particulate air) filters in seven of the nine rooms comprising the unit. Because fungal colonization of HEPA filters used to create a “protective environment” for immunocompromised patients can occur and can serve as a source for patient infections, guidelines concerning proper surveillance of these HEPA filters should be established. We suggest that before a new patient enters a “protected” room, the clean side of the HEPA filter should be cultured. If fungi are recovered from that culture, we would recommend changing the filter.

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