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Analyze and Rebuild an Apparatus to Gauge Evaporative Cooling Effectiveness of Micro-Porous Barriers.

Description: The sample used for evaporative cooling system is Fabric defender 750 with Shelltite finish. From the experimental data and equations we have diffusion coefficient of 20.9 ± 3.71 x 10-6 m2/s for fabric with one layer with 17%-20% fluctuations from the theory, 27.8 ± 4.5 x 10-6 m2/s for fabric with two layers with 6%-14% fluctuations from the theory and 24.9 ± 4.1 x 10-6 m2/s for fabric with three layers with 13%-16% fluctuations from the theory. Since the thickness of the fabric increases so the mass transport rate decreases so the mass transport resistance should be increases. The intrinsic mass resistances of Fabri-1L, Fabri-2L and Fabri-3L are respectively 104 ± 10.2 s/m, 154 ± 23 s/m and 206 ± 26 s/m from the experiment.
Date: December 2008
Creator: Mohiti Asli, Ali
Partner: UNT Libraries

Coolerado Cooler Helps to Save Cooling Energy and Dollars: New Cooling Technology Targets Peak Load Reduction

Description: This document is about a new evaporative cooling technology that can deliver cooler supply air temperatures than either direct or indirect evaporative cooling systems, without increasing humidity. The Coolerado Cooler technology can help Federal agencies reach the energy-use reduction goals of EPAct 2005, particularly in the western United States.
Date: June 1, 2007
Creator: Robichaud, R.
Partner: UNT Libraries Government Documents Department

Report on HVAC option selections for a relocatable classroom energy and indoor environmental quality field study

Description: It is commonly assumed that efforts to simultaneously develop energy efficient building technologies and to improve indoor environmental quality (IEQ) are unfeasible. The primary reason for this is that IEQ improvements often require additional ventilation that is costly from an energy standpoint. It is currently thought that health and productivity in work and learning environments requires adequate, if not superior, IEQ. Despite common assumptions, opportunities do exist to design building systems that provide improvements in both energy efficiency and IEQ. This report outlines the selection of a heating, ventilation, and air conditioning (HVAC) system to be used in demonstrating such an opportunity in a field study using relocatable school classrooms. Standard classrooms use a common wall mounted heat pump HVAC system. After reviewing alternative systems, a wall-mounting indirect/direct evaporative cooling system with an integral hydronic gas heating is selected. The anticipated advantages of this system include continuous ventilation of 100 percent outside air at or above minimum standards, projected cooling energy reductions of about 70 percent, inexpensive gas heating, improved airborne particle filtration, and reduced peak load electricity use. Potential disadvantages include restricted climate regions and possible increases in indoor relative humidity levels under some conditions.
Date: October 11, 2001
Creator: Apte, Michael G.; Delp, Woody W.; Diamond, Richard C.; Hodgson, Alfred T.; Kumar, Satish; Rainer, Leo I. et al.
Partner: UNT Libraries Government Documents Department

Guidelines for Estimating Unmetered Industrial Water Use

Description: The document provides a methodology to estimate unmetered industrial water use for evaporative cooling systems, steam generating boiler systems, batch process applications, and wash systems. For each category standard mathematical relationships are summarized and provided in a single resource to assist Federal agencies in developing an initial estimate of their industrial water use. The approach incorporates industry norms, general rules of thumb, and industry survey information to provide methodologies for each section.
Date: August 1, 2010
Creator: Boyd, Brian K.
Partner: UNT Libraries Government Documents Department

Local Climate Sensitivity of the Three Gorges Dam

Description: Two simulations, control and land use change, were performed for an eight week period (2 April-16 May 1990) to determine the net sensitivity of the local climate around the Three Gorges Dam. The analysis indicates that the large reservoir acts as a potential evaporating surface that decreases the surface temperature, cools the lower atmosphere, decreasing upward motion, and increasing sinking air mass. Such sinking results in low level moisture divergence, decreasing cloudiness, and increasing net downward radiation, which increases the surface temperature. However, results indicate that evaporative cooling dominates radiative warming in this initial study. The strong evaporation also supplies moisture to the atmosphere, suggesting an increase in precipitation, but the sinking moist air diverges away from the TGD region with no net change in precipitation. This numerical study represents an initial methodology for quantification of the impact of the Three Gorges Dam on the local climate and a more comprehensive, fine-scale set of multi-season simulations with additional observational data is needed for a more complete analysis.
Date: February 18, 2005
Creator: Miller, Norman L.; Jin, Jiming & Tsang, Chin-Fu
Partner: UNT Libraries Government Documents Department

Dew Point Evaporative Comfort Cooling: Report and Summary Report

Description: The project objective was to demonstrate the capabilities of the high-performance multi-staged IEC technology and its ability to enhance energy efficiency and interior comfort in dry climates, while substantially reducing electric-peak demand. The project was designed to test 24 cooling units in five commercial building types at Fort Carson Army Base in Colorado Springs, Colorado.
Date: November 1, 2012
Creator: Dean, J.; Herrmann, L.; Kozubal, E.; Geiger, J.; Eastment, M. & Slayzak, S.
Partner: UNT Libraries Government Documents Department

Preoperational test report, raw water system

Description: This represents the preoperational test report for the Raw Water System, Project W-030. Project W-030 provides a ventilation upgrade for the four Aging Waste Facility tanks. The system supplies makeup water to the W-030 recirculation evaporative cooling towers for tanks AY1O1, AY102, AZ1O1, AZ102. The Raw Water pipe riser and associated strainer and valving is located in the W-030 diesel generator building. The tests verify correct system operation and correct indications displayed by the central Monitor and Control System.
Date: October 29, 1997
Creator: Clifton, F.T.
Partner: UNT Libraries Government Documents Department

Review of the ALOHA code pool evaporation model

Description: The ALOHA computer code determines the evaporative mass transfer rate from a liquid pool by solving the conservation of mass and energy equations associated with the pool. As part of the solution of the conservation of energy equation, the heat flux from the ground to the pool is calculated. The model used in the ALOHA code is based on the solution of the temperature profile for a one-dimensional semi-infinite slab. This model is only valid for cases in which the boundary condition (pool temperature) is held constant. Thus, when the pool material temperature is not constant, the ALOHA ground-to-pool heat flux calculation may result in a non-conservative evaporation rate. The analytical solution for the temperature profile of a one-dimensional semi-infinite slab with a time-dependent boundary condition requires a priori knowledge of the boundary condition. Lacking such knowledge, a time-dependent finite-difference solution for the ground temperature profile was developed. The temperature gradient, and thus the ground-to-pool heat flux, at the ground-pool interface is determined from the results of the finite-difference solution. The evaporation rates over the conditions sampled using the ALOHA ground-to-pool heat flux model were up to 15% lower than those generated when the finite-difference model to calculate ground-to-pool heat flux. Overall ALOHA code estimates may compensate by judicious selection of input parameters and assumptions. Application to safety analyses thus must be performed cautiously to ensure that estimated chemical source term and its attendant downwind concentrations are bounding.
Date: November 1, 1995
Creator: Kalinich, D.A.
Partner: UNT Libraries Government Documents Department

USE OF COAL DRYING TO REDUCE WATER CONSUMED IN PULVERIZED COAL POWER PLANTS

Description: U.S. low rank coals contain relatively large amounts of moisture, with the moisture content of subbituminous coals typically ranging from 15 to 30 percent and that for lignites from 25 and 40 percent. High fuel moisture has several adverse impacts on the operation of a pulverized coal generating unit, for it can result in fuel handling problems and it affects heat rate, stack emissions and maintenance costs. Theoretical analyses and coal test burns performed at a lignite fired power plant show that by reducing the fuel moisture, it is possible to improve boiler performance and unit heat rate, reduce emissions and reduce water consumption by the evaporative cooling tower. The economic viability of the approach and the actual impact of the drying system on water consumption, unit heat rate and stack emissions will depend critically on the design and operating conditions of the drying system. The present project evaluated the low temperature drying of high moisture coals using power plant waste heat to provide the energy required for drying. Coal drying studies were performed in a laboratory scale fluidized bed dryer to gather data and develop models on drying kinetics. In addition, analyses were carried out to determine the relative costs and performance impacts (in terms of heat rate, cooling tower water consumption and emissions) of drying along with the development of optimized drying system designs and recommended operating conditions.
Date: March 1, 2006
Creator: Levy, Edward K.; Sarunac, Nenad; Bilirgen, Harun & Caram, Hugo
Partner: UNT Libraries Government Documents Department

Graphite Foam Heat Exchangers for Thermal Management

Description: Improved thermal management is needed to increase the power density of electronic and more effectively cool electronic enclosures that are envisioned in future aircraft, spacecraft and surface ships. Typically, heat exchanger cores must increase in size to more effectively dissipate increased heat loads, this would be impossible in many cases, thus improved heat exchanger cores will be required. In this Phase I investigation, MRi aimed to demonstrate improved thermal management using graphite foam (Gr-foam) core heat exchangers. The proposed design was to combine Gr-foams from POCO with MRi's innovative low temperature, active metal joining process (S-Bond{trademark}) to bond Gr-foam to aluminum, copper and aluminum/SiC composite faceplates. The results were very favorable, so a Phase II SBIR with the MDA was initiated. This had primarily 5 tasks: (1) bonding, (2) thermal modeling, (3) cooling chip scale packages, (4) evaporative cooling techniques and (5) IGBT cold plate development. The bonding tests showed that the ''reflow'' technique with S-Bond{reg_sign}-220 resulted in the best and most consistent bond. Then, thermal modeling was used to design different chip scale packages and IGBT cold plates. These designs were used to fabricate many finned graphite foam heat sinks specifically for two standard type IC packages, the 423 and 478 pin chips. These results demonstrated several advantages with the foam. First, the heat sinks with the foam were lighter than the copper/aluminum sinks used as standards. The sinks for the 423 design made from foam were not as good as the standard sinks. However, the sinks made from foam for the 478 pin chips were better than the standard heat sinks used today. However, this improvement was marginal (in the 10-20% better regime). However, another important note was that the epoxy bonding technique resulted in heat sinks with similar results as that with the S-bond{reg_sign}, slightly worse than ...
Date: June 7, 2004
Creator: Klett, J.W.
Partner: UNT Libraries Government Documents Department

Silica Extraction at Mammoth Lakes, California

Description: The purpose of this project is to develop a cost-effective method to extract marketable silica (SiO{sub 2}) from fluids at the Mammoth Lakes, California geothermal power plant. Silica provides an additional revenue source for the geothermal power industry and therefore lowers the costs of geothermal power production. The use of this type of ''solution mining'' to extract resources eliminates the need for acquiring these resources through energy intensive and environmentally damaging mining technologies. We have demonstrated that both precipitated and colloidal silica can be produced from the geothermal fluids at Mammoth Lakes by first concentrating the silica to over 600 ppm using reverse osmosis (RO). The RO permeate can be used in evaporative cooling at the plant; the RO concentrate is used for silica and potentially other resource extraction (Li, Cs, Rb). Preliminary results suggest that silica recovery at Mammoth Lakes could reduce the cost of geothermal electricity production by 1.0 cents/kWh.
Date: June 7, 2006
Creator: Bourcier, W; Ralph, W; Johnson, M; Bruton, C & Gutierrez, P
Partner: UNT Libraries Government Documents Department

Silica Extraction at the Mammoth Lakes Geothermal Site

Description: The purpose of this project is to develop a cost-effective method to extract marketable silica (SiO{sub 2}) from fluids at the Mammoth Lakes, California geothermal power plant. Marketable silica provides an additional revenue source for the geothermal power industry and therefore lowers the costs of geothermal power production. The use of this type of ''solution mining'' to extract resources from geothermal fluids eliminates the need for acquiring these resources through energy intensive and environmentally damaging mining technologies. We have demonstrated that both precipitated and colloidal silica can be produced from the geothermal fluids at Mammoth Lakes by first concentrating the silica to over 600 ppm using reverse osmosis (RO). The RO permeate can be used in evaporative cooling at the plant; the RO concentrate is used for silica and potentially other (Li, Cs, Rb) resource extraction. Preliminary results suggest that silica recovery at Mammoth Lakes could reduce the cost of geothermal electricity production by 1.0 cents/kWh.
Date: June 7, 2006
Creator: Bourcier, W; Ralph, W; Johnson, M; Bruton, C & Gutierrez, P
Partner: UNT Libraries Government Documents Department

Beneficial Reuse of San Ardo Produced Water

Description: This DOE funded study was performed to evaluate the potential for treatment and beneficial reuse of produced water from the San Ardo oilfield in Monterey County, CA. The potential benefits of a successful full-scale implementation of this project include improvements in oil production efficiency and additional recoverable oil reserves as well as the addition of a new reclaimed water resource. The overall project was conducted in two Phases. Phase I identified and evaluated potential end uses for the treated produced water, established treated water quality objectives, reviewed regulations related to treatment, transport, storage and use of the treated produced water, and investigated various water treatment technology options. Phase II involved the construction and operation of a small-scale water treatment pilot facility to evaluate the process's performance on produced water from the San Ardo oilfield. Cost estimates for a potential full-scale facility were also developed. Potential end uses identified for the treated water include (1) agricultural use near the oilfield, (2) use by Monterey County Water Resources Agency (MCWRA) for the Salinas Valley Water Project or Castroville Seawater Intrusion Project, (3) industrial or power plant use in King City, and (4) use for wetlands creation in the Salinas Basin. All of these uses were found to have major obstacles that prevent full-scale implementation. An additional option for potential reuse of the treated produced water was subsequently identified. That option involves using the treated produced water to recharge groundwater in the vicinity of the oil field. The recharge option may avoid the limitations that the other reuse options face. The water treatment pilot process utilized: (1) warm precipitation softening to remove hardness and silica, (2) evaporative cooling to meet downstream temperature limitations and facilitate removal of ammonia, and (3) reverse osmosis (RO) for removal of dissolved salts, boron, and organics. Pilot study ...
Date: July 31, 2006
Creator: Liske, Robert A.
Partner: UNT Libraries Government Documents Department

CFD MODELING ANALYSIS OF MECHANICAL DRAFT COOLING TOWER

Description: Industrial processes use mechanical draft cooling towers (MDCT's) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has a MDCT consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to conduct a parametric study for cooling tower performance under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model to achieve the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of the modeling calculations was performed to investigate the impact of ambient and operating conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was benchmarked against the literature data and the SRS test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed results will be presented here.
Date: March 3, 2008
Creator: Lee, S; Alfred Garrett, A; James02 Bollinger, J & Larry Koffman, L
Partner: UNT Libraries Government Documents Department

What`s new in building energy research - desiccant cooling program

Description: Desiccant cooling systems are energy efficient, cost effective, and environmentally safe. They are used as stand-alone systems or with conventional air-conditioning to improve the indoor air quality of all types of buildings. In these systems, a desiccant removes moisture from the air, which releases heat and increases the air temperature. The dry air is cooled using either evaporative cooling or the cooling coils of a conventional air conditioner. The absorbed moisture in the desiccant is then removed (the desiccant is regenerated, or brought back to its original dry state) using thermal energy supplied by natural gas, electricity, waste heat, or the sun. Commercially available desiccants include silica gel, activated alumina, natural and synthetic zeolites, lithium chloride, and synthetic polymers. Currently, desiccant cooling and dehumidification are being used successfully in industrial and some commercial applications. The Office of Building Technologies in the U.S. Department of Energy (DOE) is working with industry to broaden the market for desiccant cooling so its full energy savings and indoor air quality improvement potential can be realized. The main goals of the Desiccant Cooling Program are to (1) Reduce carbon dioxide emissions by 5 million tons (4.5 million metric tons) annually by 2005 and 18 million tons (16.3 million metric tons) annually by 2010. (2) Reduce energy consumption by 0.1 quad (105.5 petajoules) annually by 2005 and 0.3 quad (316.5 petajoules) annually by 2010. (3) Capture 5% of the air-conditioning market by 2005 and 15% by 2010.
Date: February 1, 1996
Partner: UNT Libraries Government Documents Department

Analysis of climatic conditions and preliminary assessment of alternative cooling strategies for houses in California transition climate zones

Description: This is a preliminary scoping study done as part of the {open_quotes}Alternatives to Compressive Cooling in California Transition Climates{close_quotes} project, which has the goal of demonstrating that houses in the transitional areas between the coast and the Central Valley of California do not require air-conditioning if they are properly designed and operated. The first part of this report analyzes the climate conditions within the transitional areas, with emphasis on design rather than seasonal conditions. Transitional climates are found to be milder but more variable than those further inland. The design temperatures under the most stringent design criteria, e.g. 0.1 % annual, are similar to those in the Valley, but significantly lower under more relaxed design criteria, e.g., 2% annual frequency. Transition climates also have large day-night temperature swings, indicating significant potential for night cooling, and wet-bulb depressions in excess of 25 F, indicating good potential for evaporative cooling. The second part of the report is a preliminary assessment using DOE-2 computer simulations of the effectiveness of alternative cooling and control strategies in improving indoor comfort conditions in two conventional Title-24 houses modeled in various transition climate locations. The cooling measures studied include increased insulation, light colors, low-emissivity glazing, window overhangs, and exposed floor slab. The control strategies studied include natural and mechanical ventilation, and direct and two-stage evaporative cooling. The results indicate the cooling strategies all have limited effectiveness, and need to be combined to produce significant improvements in indoor comfort. Natural and forced ventilation provide similar improvements in indoor conditions, but during peak cooling periods, these will still be above the comfort zone. Two-stage evaporative coolers can maintain indoor comfort at all hours, but not so direct evaporative coolers.
Date: July 1, 1995
Creator: Huang, Y.J. & Zhang, H.
Partner: UNT Libraries Government Documents Department

Energy and indoor environmental quality in relocatable classrooms

Description: Relocatable classrooms (RCs) are commonly utilized by school districts with changing demographics and enrollment sizes. Four energy-efficient RCs were designed and constructed for this study to demonstrate technologies that simultaneously attempt to improve energy efficiency and indoor environmental quality (IEQ). Two were installed at each of two school districts, and energy use and IEQ parameters were monitored during occupancy. Two (one per school) were finished with materials selected for reduced emissions of toxic and odorous volatile organic compounds (VOCs). Each RC had two HVAC systems, alternated weekly, consisting of a standard heat-pump system and an indirect-direct evaporative cooling (IDEC) system with gas-fired hydronic heating. The hypothesized advantages of the IDEC include continuous outside air ventilation at {ge}7.5 L s{sup -1} per person, {approx}70% less cooling energy and efficient particle filtration. Measurements include: carbon dioxide, particles, VOCs, temperature, humidity, thermal comfort, noise, meteorology, and energy use. Preliminary IEQ monitoring results are reported.
Date: February 1, 2002
Creator: Apte, Michael; Hodgson, Alfred; Shendell, Derek; Dibartolomeo, Dennis; Hochi, Toshifumi; Kumar, Satish et al.
Partner: UNT Libraries Government Documents Department

Impact of ambient pressure on performance of desiccant cooling systems

Description: The impact of ambient pressure on the performance of the ventilation cycle desiccant cooling system and its components was studied using computer simulations. The impact of ambient pressure depended on whether the system was designed for fixed-mass flow rate or fixed-volume flow rate operation. As ambient pressure decreased from 1.0 to 0.8 atm, the system thermal coefficient of performance increased by 8% for both fixed-mass and fixed-volume flow rate, the cooling capacity of the system (in kW) was decreased by 14% for the fixed-volume flow rate system and increased by 7% for the fixed-mass flow rate system, the electric power requirements for the system with fixed-volume flow rate did not change, and the electric power requirement for the fixed-mass flow rate system increased by 44%. The overall coefficient of performance increased up to 5% for the fixed-volume flow rate systems, and decreased up to 4% for the fixed-mass flow rate system. 16 refs.
Date: December 1, 1991
Creator: Pesaran, A. A.
Partner: UNT Libraries Government Documents Department

NREL's Energy-Saving Technology for Air Conditioning Cuts Peak Power Loads Without Using Harmful Refrigerants (Fact Sheet)

Description: This fact sheet describes how the DEVAP air conditioner was invented, explains how the technology works, and why it won an R&D 100 Award. Desiccant-enhanced evaporative (DEVAP) air-conditioning will provide superior comfort for commercial buildings in any climate at a small fraction of the electricity costs of conventional air-conditioning equipment, releasing far less carbon dioxide and cutting costly peak electrical demand by an estimated 80%. Air conditioning currently consumes about 15% of the electricity generated in the United States and is a major contributor to peak electrical demand on hot summer days, which can lead to escalating power costs, brownouts, and rolling blackouts. DEVAP employs an innovative combination of air-cooling technologies to reduce energy use by up to 81%. DEVAP also shifts most of the energy needs to thermal energy sources, reducing annual electricity use by up to 90%. In doing so, DEVAP is estimated to cut peak electrical demand by nearly 80% in all climates. Widespread use of this cooling cycle would dramatically cut peak electrical loads throughout the country, saving billions of dollars in investments and operating costs for our nation's electrical utilities. Water is already used as a refrigerant in evaporative coolers, a common and widely used energy-saving technology for arid regions. The technology cools incoming hot, dry air by evaporating water into it. The energy absorbed by the water as it evaporates, known as the latent heat of vaporization, cools the air while humidifying it. However, evaporative coolers only function when the air is dry, and they deliver humid air that can lower the comfort level for building occupants. And even many dry climates like Phoenix, Arizona, have a humid season when evaporative cooling won't work well. DEVAP extends the applicability of evaporative cooling by first using a liquid desiccant-a water-absorbing material-to dry the air. The ...
Date: July 1, 2012
Partner: UNT Libraries Government Documents Department

HEAVY ION FUSION SCIENCE VIRTUAL NATIONAL LABORATORY 4th QUARTER 2008 MILESTONE REPORT

Description: This milestone has been met. In the previous quarter (3rd quarter FY2008), the Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) completed the new experimental target chamber facility for future Warm Dense Matter (WDM) experiments [1]. The target chamber is operational and target experiments are now underway, using beams focused by a final focus solenoid and compressed by an improved bunching waveform. Initial experiments have demonstrated the capability of the Neutralized Drift Compression Experiment (NDCX) beam to heat bulk matter in target foils. The experiments have focused on tuning and characterizing the NDCX beam in the target chamber, implementing the target assembly, and implementing target diagnostics in the target chamber environment. We have completed a characterization and initial optimization of the compressed and uncompressed NDCX beam entering the target chamber. The neutralizing plasma has been significantly improved to increase the beam neutralization in the target chamber. Preliminary results from recent beam tests of a gold cone for concentrating beam energy on target are encouraging and indicate the potential to double beam intensity on target. Other advantages of the cone include the large amount of neutralizing secondary electrons expected from the grazing incidence at the cone walls, and the shielding of the target from the edges of the beam pulse. The first target temperature measurements with the fast optical pyrometer were made on Sep. 12, 2008. The fast optical pyrometer is a unique and significant new diagnostic. These new results demonstrate for the first time beam heating of the target to a temperature well over 2000 K. The initial experimental results are suggestive of potentially interesting physics. The rapid initial rise and subsequent decay of the target temperature during the beam pulse indicate changes in the balance of beam heating and target evaporative cooling, a behavior which may be affected by ...
Date: September 16, 2008
Creator: Bieniosek, F.M.; Anders, A.; Barnard, J.J.; Dickinson, M.R.; Greenway, W.; Henestroza, E. et al.
Partner: UNT Libraries Government Documents Department

Implementing Strategies for Drying and Pressing Wood Without Emissions Controls

Description: Drying and pressing wood for the manufacture of lumber, particleboard, oriented strand board (OSB), veneer and medium density fiberboard (MDF) release volatile organic compounds (VOCs) into the atmosphere. These emissions require control equipment that are capital-intensive and consume significant quantities of natural gas and electricity. The objective of our work was to understand the mechanisms through which volatile organic compounds are generated and released and to develop simple control strategies. Of the several strategies developed, two have been implemented for OSB manufacture over the course of this study. First, it was found that increasing final wood moisture by about 2-4 percentage points reduced the dryer emissions of hazardous air pollutants by over 70%. As wood dries, the escaping water evaporatively cools the wood. This cooling tapers off wood when the wood is nearly dry and the wood temperature rises. Thermal breakdown of the wood tissue occurs and VOCs are released. Raising the final wood moisture by only a few percentage points minimizes the temperature rise and reduces emissions. Evaporative cooling also impacts has implications for VOC release from wood fines. Flaking wood for OSB manufacture inevitable generates fines. Fines dry out rapidly because of their high surface area and evaporative cooling is lost more rapidly than for flakes. As a result, fines emit a disproportionate quantity of VOCs. Fines can be reduced in two ways: through screening of the green furnish and through reducing their generation during flaking. The second approach is preferable because it also increased wood yield. A procedure to do this by matching the sharpness angle of the flaker knife to the ambient temperature was also developed. Other findings of practical interests are as follows: Dielectric heating of wood under low-headspace conditions removes terpenes and other extractives from softwood; The monoterpene content in trees depend upon temperature ...
Date: September 7, 2007
Creator: Banerjee, Sujit & Conners, Terrance
Partner: UNT Libraries Government Documents Department