Overheating and Frequent Thermal Cycling of Outdoor Electronic Cabinets in Cold Climates

1999 ◽  
Vol 121 (1) ◽  
pp. 50-54 ◽  
Author(s):  
E. B. Zimmerman ◽  
H. Hegab ◽  
G. T. Colwell
Keyword(s):  
Thermal Cycling ◽  
Cooling System ◽  
Experimental Testing ◽  
Low Cost ◽  
Effective Means ◽  
Axial Flow ◽  
Ambient Air ◽  
Low Flow ◽  
Transient Temperature ◽  
Forced Air

Telephone companies use electronics to route calls between customers. The electronics are generally closely packed together and placed in steel containers outdoors. Forced air convection utilizing the outside ambient air is an effective means to cool outdoor electronic cabinets and is generally the system of choice given the relatively low cost and simplicity when compared to alternative cooling methods. Simple axial flow fans are typically turned on and off by a thermostat located inside the cabinet to keep the inside air temperature below a predetermined maximum. This simple cooling system is usually effective during summer operations. However, it may result in overheating and excessive thermal cycling in winter operations. Transient temperature data from experiments on a telecommunications cabinet is presented illustrating this problem. One possible solution to this problem is using continuously operating fans at low flow rates. This solution was arrived at through a combination of experimental testing and numerical simulation.

Desiccant Degradation in Desiccant Cooling Systems: An Experimental Study

1993 ◽  
Vol 115 (4) ◽  
pp. 212-219 ◽  
Author(s):  
A. A. Pesaran
Keyword(s):  
Thermal Cycling ◽  
Silica Gel ◽  
Molecular Sieves ◽  
Cooling System ◽  
Ambient Air ◽  
Activated Alumina ◽  
Humid Air ◽  
Cooling Systems ◽  
Degradation Data ◽  
Capacity Loss

We conducted experiments to quantify the effects of thermal cycling and exposure to contamination on solid desiccant materials that may be used in desiccant cooling systems. The source of contamination was cigarette smoke, which is considered one of the worst pollutants in building cooling applications. We exposed five different solid desiccants to “ambient” and “contaminated” humid air: silica gel, activated alumina, activated carbon, molecular sieves, and lithium chloride. We obtained the moisture capacity of samples as a function of exposure time. Compared to virgin desiccant samples, the capacity loss caused by thermal cycling with humid ambient air was 10 percent to 30 percent for all desiccants. The capacity loss because of combined effect of thermal cycling with “smoke-filled” humid air was between 30 percent to 70 percent. The higher losses occurred after four months of experiment time, which is equivalent to four to eight years of field operation. Using a system model and smoke degradation data on silica gel, we predicted that, for low-temperature regeneration, the loss in performance of a ventilation-cycle desiccant cooling system would be between 10 percent to 35 percent, in about eight years, with higher value under worst conditions.

High Reliability Flip Chip Using Low CTE Laminate Substrates

2005 ◽  
Author(s):  
D. Scott Copeland ◽  
M. Kaysar Rahim ◽  
Jeffrey C. Suhling ◽  
Guoyun Tian ◽  
Pradeep Lall ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Thermal Cycling ◽  
Flip Chip ◽  
Experimental Testing ◽  
High Reliability ◽  
Low Cost ◽  
Substrate Material ◽  
Space Applications ◽  
Sandwich Construction ◽  
Test Chips

In this work, we report on our efforts to develop high reliability flip chip on laminate assemblies for deployment in harsh thermal cycling environments characteristic of ground and aerospace vehicles (e.g. −55 to 150 °C). Reliability enhancement has been achieved through the use of a novel low expansion, high stiffness, and relatively low cost laminate substrate material that virtually eliminates CTE mismatches between the silicon die and top layer PCB interconnect. The utilized laminate features a sandwich construction that contains standard FR-406 outer layers surrounding a low expansion high thermal conductivity carbon fiber-reinforced composite core (STABLCOR®). Through both experimental testing and modeling, we have demonstrated that robust flip chip assemblies can be produced that illustrate ultra-high solder joint reliability during thermal cycling and extremely low die stresses. Liquid to liquid thermal shock testing has been performed on test assemblies incorporating daisy chain test die, and piezoresistive test chips have been used to characterize temperature dependent die stresses. In both sets of experiments, results obtained using the hybrid PCB laminate with FR-406 outer layers and carbon fiber core have been compared to those obtained with more traditional glass-epoxy laminate substrates including FR-406 and NELCO 4000-13. Nonlinear finite element modeling results for the low expansion flip chip on laminate assemblies have been correlated with the experimental data. Unconstrained thermal expansion measurements have also been performed on the hybrid laminate materials using strain gages to demonstrate their low CTE characteristics. Other experimental testing has demonstrated that the new laminate successfully passes toxicity, flammability, and vacuum stability testing as required for pressurized and un-pressurized space applications.

A Low-cost, Portable, Forced-air Pallet Cooling System

1993 ◽  
Vol 9 (1) ◽  
pp. 97-104 ◽  
Author(s):  
M. D. Boyette ◽  
R. P. Rohrbach
Keyword(s):  
Cooling System ◽  
Low Cost ◽  
Forced Air

Flow Structure in Continuous Flow Electrophoresis Chambers

1981 ◽  
Vol 9 ◽  
Author(s):  
J. A. DEIBER ◽  
D. A. Saville
Keyword(s):  
Continuous Flow ◽  
Cooling System ◽  
Finite Difference Methods ◽  
Axial Flow ◽  
Approximate Solutions ◽  
Low Flow ◽  
Small Temperature ◽  
Higher Power ◽  
Hydrodynamic Processes ◽  
Electro Osmotic Flow

ABSTRACTThere are at least two ways that hydrodynamic processes can limit continuous flow electrophoresis. One arises from the sensitivity of the flow to small temperature gradients, especially at low flow rates and power levels. This sensitivity can be suppressed, at least in principle, by providing a carefully tailored, stabilizing temperature gradient in the cooling system that surrounds the flow channel. At higher power levels another limitation arises due to a restructuring of the main flow. This restructuring is caused by buoyancy, which is in turn affected by the electro-osmotic crossflow. Approximate solutions to appropriate partial differential equations have been computed by finite difference methods. One set of results is described here to illustrate the strong coupling between the structure of the main (axial) flow and the electro-osmotic flow.

Experimental Investigation of a Combined Photovoltaic Thermal System via Air Cooling for Summer Weather of Egypt

2020 ◽  
Vol 12 (4) ◽  
Author(s):  
Hussein M. Maghrabie ◽  
A. S. A. Mohamed ◽  
M. Salem Ahmed
Keyword(s):  
Cooling System ◽  
Electrical Power ◽  
Ambient Air ◽  
Critical Issue ◽  
Air Cooling ◽  
Pv Panel ◽  
Current Implementation ◽  
Air Cooling System ◽  
Forced Air ◽  
Electrical Power Output

Abstract Utilizing photovoltaic (PV) panels for generating electrical power is accompanied with a low electrical efficiency that is further reduced as its surface temperature surpasses an acceptable limit. In order to overcome this critical issue, it is necessary to maintain the PV panels relatively at low surface temperatures as possible as using appropriate cooling systems. The current implementation assesses experimentally the performance of a combined PV thermal (PV/T) system using a forced-air cooling system during April, May, June, and July of summer weather of Egypt. The results reveal that the highest values of the solar intensity and the ambient air temperature are obtained in July. Employing the forced-air cooling system reduces the average temperature on the front and back sides of the PV panel during July by 12% and 12.8%, respectively. In addition, the forced-air cooling system enhances noticeably the electrical power output of the PV panel by 3.3%, 4.3%, 4.5%, and 6.1% during April, May, June, and July, respectively. Moreover, the maximum value of the average thermal efficiency achieved during July is 37%; whereas, the corresponding value of the average overall efficiency fulfilled during April is 48.7%.

A Liquid Desiccant System for Solar Cooling and Dehumidification

2004 ◽  
Vol 126 (3) ◽  
pp. 879-885 ◽  
Author(s):  
K. Gommed ◽  
G. Grossman
Keyword(s):  
Direct Contact ◽  
Cooling System ◽  
Low Cost ◽  
Cooling Water ◽  
Ambient Air ◽  
Low Grade ◽  
Liquid Desiccant ◽  
Flow Rates ◽  
Heating And Cooling ◽  
Air Stream

The growing demand for air conditioning, particularly in hot and humid climates has caused a significant increase in demand for energy resources. A promising solar technology with potential to alleviate the problem is an open absorption system, where humidity is absorbed directly from the air to be treated by direct contact with the absorbent. The absorbent is then regenerated, again in direct contact with an external air stream, at relatively low temperatures of the heat source. The paper describes a study of a liquid desiccant cooling system designed to air-condition a group of offices on the top floor of a building in the Mediterranean city of Haifa, Israel. The system is capable of using as its source of power low-grade solar heat, of the type obtainable from low-cost flat plate collectors, and has a potential to provide both cooling and dehumidification in variable ratios, as required by the load. Several cycle variations have been considered, corresponding to different design options. A parametric study shows that entrance conditions of the ambient air significantly affect the heat and mass transfer occurring during the dehumidification process. The temperatures and flow rates of the heating and cooling water and the flow rates of solution through the dehumidifier and regenerator affect the humidity of the supply air delivered to the conditioned space, and show an optimum in certain cases.

scholarly journals Deployment, Calibration, and Cross-Validation of Low-Cost Electrochemical Sensors for Carbon Monoxide, Nitrogen Oxides, and Ozone for an Epidemiological Study

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4214
Author(s):  
Christopher Zuidema ◽  
Cooper S. Schumacher ◽  
Elena Austin ◽  
Graeme Carvlin ◽  
Timothy V. Larson ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Exposure Assessment ◽  
Epidemiological Study ◽  
Electrochemical Sensors ◽  
Low Cost ◽  
Puget Sound ◽  
Ambient Air ◽  
Ambient Air Pollution ◽  
Calibration Models ◽  
Study Participants

We designed and built a network of monitors for ambient air pollution equipped with low-cost gas sensors to be used to supplement regulatory agency monitoring for exposure assessment within a large epidemiological study. This paper describes the development of a series of hourly and daily field calibration models for Alphasense sensors for carbon monoxide (CO; CO-B4), nitric oxide (NO; NO-B4), nitrogen dioxide (NO2; NO2-B43F), and oxidizing gases (OX-B431)—which refers to ozone (O3) and NO2. The monitor network was deployed in the Puget Sound region of Washington, USA, from May 2017 to March 2019. Monitors were rotated throughout the region, including at two Puget Sound Clean Air Agency monitoring sites for calibration purposes, and over 100 residences, including the homes of epidemiological study participants, with the goal of improving long-term pollutant exposure predictions at participant locations. Calibration models improved when accounting for individual sensor performance, ambient temperature and humidity, and concentrations of co-pollutants as measured by other low-cost sensors in the monitors. Predictions from the final daily models for CO and NO performed the best considering agreement with regulatory monitors in cross-validated root-mean-square error (RMSE) and R2 measures (CO: RMSE = 18 ppb, R2 = 0.97; NO: RMSE = 2 ppb, R2 = 0.97). Performance measures for NO2 and O3 were somewhat lower (NO2: RMSE = 3 ppb, R2 = 0.79; O3: RMSE = 4 ppb, R2 = 0.81). These high levels of calibration performance add confidence that low-cost sensor measurements collected at the homes of epidemiological study participants can be integrated into spatiotemporal models of pollutant concentrations, improving exposure assessment for epidemiological inference.

scholarly journals Air circulation in a gastrointestinal light source box and endoscope in the era of SARS-CoV-2 and airborne transmission of microorganisms

2021 ◽  
Vol 09 (03) ◽  
pp. E482-E486
Author(s):  
Stanislas Chaussade ◽  
Einas Abou Ali ◽  
Rachel Hallit ◽  
Arthur Belle ◽  
Maximilien Barret ◽  
...  
Keyword(s):  
Light Source ◽  
Cooling System ◽  
Air Cooling ◽  
Airborne Transmission ◽  
Plastic Tube ◽  
Care Workers ◽  
Air Cooling System ◽  
Forced Air ◽  
Air Circulation ◽  
Closed Environment

Abstract Background and study aims The role that air circulation through a gastrointestinal endoscopy system plays in airborne transmission of microorganisms has never been investigated. The aim of this study was to explore the potential risk of transmission and potential improvements in the system. Methods We investigated and described air circulation into gastrointestinal endoscopes from Fujifilm, Olympus, and Pentax. Results The light source box contains a lamp, either Xenon or LED. The temperature of the light is high and is regulated by a forced-air cooling system to maintain a stable temperature in the middle of the box. The air used by the forced-air cooling system is sucked from the closed environment of the patient through an aeration port, located close to the light source and evacuated out of the box by one or two ventilators. No filter exists to avoid dispersion of particles outside the processor box. The light source box also contains an insufflation air pump. The air is sucked from the light source box through one or two holes in the air pump and pushed from the air pump into the air pipe of the endoscope through a plastic tube. Because the air pump does not have a dedicated HEPA filter, transmission of microorganisms cannot be excluded. Conclusions Changes are necessary to prevent airborne transmission. Exclusive use of an external CO2 pump and wrapping the endoscope platform with a plastic film will limit scatter of microorganisms. In the era of pandemic virus with airborne transmission, improvements in gastrointestinal ventilation systems are necessary to avoid contamination of patients and health care workers.

scholarly journals Room-Temperature Solution-Processed 0D/1D Bilayer Electrodes for Translucent CsPbBr3 Perovskite Photovoltaics

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1489
Author(s):  
Bhaskar Parida ◽  
Saemon Yoon ◽  
Dong-Won Kang
Keyword(s):  
Solar Cells ◽  
Indium Tin Oxide ◽  
High Performance ◽  
Room Temperature ◽  
Low Cost ◽  
Perovskite Solar Cells ◽  
Ambient Air ◽  
Plasma Damage ◽  
Temperature Solution ◽  
Ito Nanoparticles

Materials and processing of transparent electrodes (TEs) are key factors to creating high-performance translucent perovskite solar cells. To date, sputtered indium tin oxide (ITO) has been a general option for a rear TE of translucent solar cells. However, it requires a rather high cost due to vacuum process and also typically causes plasma damage to the underlying layer. Therefore, we introduced TE based on ITO nanoparticles (ITO-NPs) by solution processing in ambient air without any heat treatment. As it reveals insufficient conductivity, Ag nanowires (Ag-NWs) are additionally coated. The ITO-NPs/Ag-NW (0D/1D) bilayer TE exhibits a better figure of merit than sputtered ITO. After constructing CsPbBr3 perovskite solar cells, the device with 0D/1D TE offers similar average visible transmission with the cells with sputtered ITO. More interestingly, the power conversion efficiency of 0D/1D TE device was 5.64%, which outperforms the cell (4.14%) made with sputtered-ITO. These impressive findings could open up a new pathway for the development of low-cost, translucent solar cells with quick processing under ambient air at room temperature.

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