Dryers' Classifications and selection (original) (raw)
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Heat pump dryers are applied for heat sensitive materials due its controllable drying conditions. It saves energy and is more environmentally friendly than conventional direct or indirect heated dryers. In Norway, R&D on this technology has been conduted over a period of more than 20 years that resulted in industrial applications. Materials like fish products, fruits, vegetables, dairy, biological active and heat sensitive materials have been dried in test plants. Typical quality controlled parameters are color, taste, density and rehydration properties. This paper covers design, energy consumption, operation modes and criteria and influence of product quality of heat pump dryers as well as the interaction between drying chamber and dryer operation. Heat pump systems with different natural working fluids are simulated at different drying conditions and evaporating temperatures. Consequences on the dryer thermal efficiency and the heat pump coefficient of performance are studied at different operational modes. Quality and energy use at different drying modes for several food products and chemical pulp are studied.
Comparison of energy parameters in various dryers
Energy Conversion and Management, 2014
This study aimed at investigating the energy output, thermal output, drying efficiency and specific energy in various drying methods for drying of chamomile. These methods included convective, infrared, convectiveinfrared, microwave, microwave-convective, microwave-vacuum, vacuum, and hybrid photovoltaicthermal solar (with/without heat pump). Results of data analysis showed that the highest energy output of 49.99% belonged to the microwave dryer, while the lowest 1.41% belonged to the vacuum dryer. Moreover, the maximum and minimum thermal outputs being 78.22% and 2.68% were associated with the vacuum-microwave and vacuum dryers, respectively. In the hot-air-related dryers, drying efficiency increased with temperature. In microwave-related dryers, however, drying efficiency first increased (up to a microwave power of 300 W) and then decreased with further increase in microwave power. Assessment of the specific energy requirement in various dryers showed that the highest and lowest values belonged to the vacuum and microwave methods with 318.42 and 4.32 MJ/kg w , respectively. Additionally, results of analysis indicated that adding a heat pump to the photovoltaic solar dryer increases drying efficiency, energy output and thermal output, while it reduces the required specific energy.
Experimental dryer design for agricultural products
Engenharia Agrícola, 2016
This study consisted of designing and building an experimental dryer that allows working with different temperatures and velocities of the air, aiming to perform studies on thin-and thick-layer drying of agricultural products. The project was divided into three stages: heat source designing, dryer geometric parameters, and fan selection to meet operational demand. Heating was made by a set of six electrical resistances totaling 12 kW and the drying bed in thin layer was composed of two trays with diameter of 0.20 m. Operational demands were met using a centrifugal fan with a power rating of 735.5 W. The used methodology was able to size the experimental dryers for thin-and thick-layer drying working at distinct temperatures and air velocities.
Low Temperature Drying with Heat Pumps New Generations of High Quality Dried Products
2003
Heat pump dryers have found their application in drying of heat sensitive materials due to the possibilities of controlling drying conditions. In addition, this technology is energy saving and more environmentally friendly than direct heated dryers. In Norway, research on this technology has taken place over a period of 20 years and several industrial applications are seen, like drying of fish and vegetables. Several products have been dried in test plants, like fish products, fruits, vegetables, dairy products, biological active products and other heat sensitive materials. For such products quality can be controlled, like color, taste, bulk density and rehydration properties.
Energy Effective and Green Drying Technologies with Industrial Applications
Chemical engineering transactions, 2018
Heat pump drying is a green technology with zero global warming potential and zero ozone depletion potential when operating with natural fluids. A well designed heat pump dryer can be several times more energy efficient and less costly than conventional dryers. This dryer beneficially contributes to a sustainable society while providing superior products at competitive cost. It is an advanced engineered drying technology ready for implementation by modern industries wishing a return of investment while contributing to a sustainable society. This paper covers the advances in heat pump and superheated steam drying technologies. These drying processes are in the category of green technologies because they are highly effective and advantageous for the environment and climate change. Descriptions and layouts are given covering design of heat pump and steam dryers. Details are provided in their beneficial operation in single and multistage with vapor compression and drying chambers placed in series. The drying modes covered are atmospheric sublimation and evaporation for improved capacity and superior characteristics of dried materials. The future trend is heat pump drying with natural fluids and superheated steam drying complying with proper industrial practice and with regulations reducing damage to sea, soil and water as well as zeroing contribution to global warming and to climate change. These technologies have been built and extensive R&D has been done at Norwegian University of Science and Technology in Trondheim. The technology has progressed to pilot scale and industrial applications indicating a small but real contribution to a better society today and tomorrow. Lastly, this is an advanced engineered drying technology ready for implementation by modern industries wishing a return of investment while preserving the environment.
Drying Technology: An International Journal
2014
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