Heat exchangers
Heat exchangers are used for heating, cooling, evaporation or condensation of media at different temperatures. The basic function is to transfer the thermal energy of a medium with a higher temperature level to a medium with a lower temperature level.
Convective heat transfer refers to the transfer of heat between a surface and a fluid. Convective heat transfer processes are associated with fluid flow movements, i.e. convection.
Convective heat transfer in heat exchangers with different geometries
Learning objectives/experiments
- interplay between Nusselt number, Reynolds number and heat flow
- measurement of pressure distribution in the air duct and development of the velocity profile
- measurement of convective heat transfer in the tube bundle as a function of position
- pressure loss across the tube bundle
- measurement of convective heat transfer with free convection in the air duct (chimney effect)
In recuperators, two media flow through simultaneously in a steady state. There is a partition between the media flows, which serves as a transfer surface. The heat is transferred indirectly from the hot medium to the partition and from the partition to the cold medium, without time lag.
Measuring the transfer characteristics of five different heat exchanger models, system control via PLC
Learning objectives/experiments
- in conjunction with a heat exchanger (WL 110.01 to WL 110.05)
- plotting temperature curves
- determining the mean heat transfer coefficient
- comparing different heat exchanger types
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Transparent heat exchanger with additional temperature measuring point after half of the transfer section; parallel flow and counterflow operation
Learning objectives/experiments
- in conjunction with WL 110 supply unit
- function and behaviour during operation of a tubular heat exchanger
- plotting temperature curves:
in parallel flow operation
in counterflow operation
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Typical plate heat exchanger in parallel flow and counterflow operation
Learning objectives/experiments
- in conjunction with WL 110 supply unit
- function and behaviour during operation of a plate heat exchanger
- plotting temperature curves:
in parallel flow operation
in counterflow operation
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Transparent shell and tube heat exchanger in cross parallel flow and cross counterflow operation
Learning objectives/experiments
- in conjunction with WL 110 supply unit
- function and behaviour during operation of shell and tube heat exchanger
- plotting temperature curves:
in cross parallel flow operation
in cross counterflow operation
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Heating using jacket or coiled tube; stirrer for improved mixing of medium
Learning objectives/experiments
- in conjunction with WL 110 supply unit
- function and behaviour during operation of a stirred tank with double jacket and coil
- plotting time functions:
heating mode with jacket
heating mode with coiled tube
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Heat transfer between water and air; cross-flow operation
Learning objectives/experiments
- in conjunction with WL 110 supply unit
- function and behaviour of a finned tube heat exchanger
- determine the mean heat transfer coefficient
- influence of heat capacity
- compare with other heat exchanger types
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Function of the heat exchanger as an air heater or water cooler
Learning objectives/experiments
- familiarisation with the heat transfer process between water and air
- determination of heat flows from water and air
- determination of the efficiency or losses
- energy balances at the heat exchanger
- plot pump characteristic
Heat transfer in pipe flows and determination of heat flux; parallel flow and counterflow operation
Learning objectives/experiments
- record temperature curves
- in parallel flow mode
- in counterflow mode
- determine average heat flux for parallel flow and counterflow operation
- determine average overall heat transfer coefficients
Heat exchanger with measurement of the fluid and wall temperature; operation in parallel flow and counterflow
Learning objectives/experiments
- record temperature curves
- in parallel flow mode
- in counterflow mode
- convective heat transfer on pipe walls and in the flow
- influence of mass flows on the temperature profile
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Convective heat transfer using shell & tube and finned tube heat exchangers
Learning objectives/experiments
- experiments without accessories
- recording the fan characteristic
- velocity distribution in the air duct
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Heat transfer process between steam and water, determination of heat flux of steam and water
Learning objectives/experiments
- familiarisation with the heat transfer process between steam and water
- determine of heat flux of steam and water
- determine the efficiency or losses
- determine the overall heat transfer coefficient
Direct-contact heat exchangers bring two media with different temperatures into contact and mix them together. The heat and mass transfer takes place directly.
Principle of operation and characteristic variables of a wet cooling tower with forced ventilation
Learning objectives/experiments
- thermodynamic principles of the wet cooling tower
- changes of state of the air in the h-x diagram
- determination of the cooling capacity
- energy balances
- calculation of process parameters, such as maximum cooling distance, cooling zone width etc.
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One special feature is the heat transfer by means of fluidised bed technology, which is investigated using a fluidised bed reactor.
Heat transfer from a heating element to the fluidised bed
Learning objectives/experiments
- basic information on the fluidisation of fixed beds
- pressure curve within the bed
- pressure losses depending on
- flow velocity
- particle size of the bulk solid
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