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Drying with heat exchangers (radiators)

Garlic can be dried by heating up the process air with heat exchangers (radiators) connected to one central boiler or boilers.

Example of 3 small modular boilers connected by a cascade arrangement.

Example of 1 large modular boiler

In the case of a central boiler, water is warmed up and brought to the heat exchange unit via pipes (to and return).

Heating unit with: Battery or radiator, Pump, 3 away mixing valve with engine (right top)

The warm water warms up the radiator (with thin slats).

Air sucked through the radiators is brought to the correct temperature by the radiator.

A pump ensures that water is pumped continuously through the radiator.

When the air needs to be warmed further, a three-way mixing valve is gradually opened.

Hot water from the boiler heats up the radiator even more, heating up the air. The ABC processor automatically ensures the supply of boiler air is high at a large temperature difference; and lowers flow when a smaller difference is measured. This ensures that a constant desired air temperature is quickly reached.

The ABC processor controls 1 or more modular boilers. In the case of heat demand, the first boiler is started at minimum capacity. In the case of increasing demand, the capacity is automatically increased and possibly a2nd, 3rd etc boiler is started.

Geconditioneerd drogen van knoflook; droger door afkoelen en weer opwarmen van de proceslucht. Dankzij sterk afkoelen wordt vocht door condensatie uit de proceslucht onttrokken. Vervolgens wordt de lucht weer opgewarmd zodat weer vocht kan worden geadsorbeerd. Er kan dan bij lagere temperaturen voldoende vocht worden opgenomen.

Drying with dried air by condensation

A system in which the process air in the evaporator is cooled by a cooling medium (liquid to gas) and is reheated by hot water in a heating battery. The released energy when cooling is transferred to water after the evaporator via a plate heat exchange of the hot gas.

Plate Heat Exchanger; energy from gas passes to water

This indirect system has a loss of about 4-5% on energy due to heat transmission from gas to water. However, this is more than compensated by the fact that excess energy (heat) can be issued in other places; other drying sections or heating up areas or floors.

The hot water is buffered in an insulated tank. A water buffer ensures that the temperature of the water is stable and can also be used at a later date.

From the central water buffer, hot water can be easily transported to different places via pipes.

Example of an ABC line page with the central tank and flow of hot gas (right) and hot water

At the drying sections, hot water is added to the radiator. With a modular 3-way mixing valve, the correct amount of hot water is fed by the radiator. The desired temperature can be achieved and maintained perfectly.

Excess energy (during cooling) can be used to:

  • warm up offices and processing rooms.
  • warm floors (dry)
  • keep dock shelters frost-free
  • Etc.

 

In the Netherlands, in new business premises (with winter cooling);  the floor is often equipped as a condenser. Power for the condenser fans is no longer necessary (no noise) and the floor remains dry and warm in winter.

Principle of indirect operation; hot gas is cooled in the plate exchanger by allowing energy from cooling to the water. The warm water flows through a water buffer to heating batteries (radiators) where the process air is warmed up. Colder water flows via the buffer vessel and returns to the plate changer where the water is warmed up again.
When drying condensation, a part of the energy is often excess. During cooling, all energy must be drained. With the indirect principle, the energy can be easily dispensed via hot water for heating offices, processing rooms, floors (dry), loading floors etc. This makes the system very profitable.
By maximizing the use of the released energy, the indirect method is ultimately very energy efficient. This energy-efficient method is very practical and is therefore widely applied.

Because the indirect method is most applied, I will explain it further.