A Compact and Efficient Solution for Direct Tank Heating

In many industrial processes, alkaline liquids need to be maintained at a controlled temperature to ensure stable process 

performance. Traditional heating systems may require external heat exchangers, circulation pumps and additional piping, resulting 

in a larger system footprint and higher installation and maintenance requirements.

A fully welded Pillow Plate Coil Bank provides an alternative solution: the heat exchanger can be directly immersed in the alkaline

 liquid tank, allowing heat to be transferred directly from the heating medium to the process liquid.

Application Overview

In this application, a Pillow Plate Coil Bank is installed directly inside an alkaline liquid tank.

The heating medium is steam, which flows through the internal channels of the Pillow Plate coils. The coil bank transfers heat 

through the stainless-steel plates to the surrounding alkaline liquid.

This direct immersion configuration creates a simple and compact heat-transfer system while eliminating the need for a separate 

external heat exchanger.

Key Design Parameters

Parameter                                                                                                                                      Design Value

Heating medium                                                                                                                                  Steam

Steam inlet temperature                                                                                                                    150°C

Condensate outlet temperature                                                                                                        70°C

Process medium                                                                                                                                Alkaline liquid

Process liquid inlet temperature                                                                                                         30°C

Process liquid outlet temperature                                                                                                         60°C

Thermal duty                                                                                                                                207,011 kcal/h

Heat transfer area                                                                                                                             10.91 m²

Design pressure                                                                                                                                1,300 kPa(g)

Design temperature                                                                                                                              200°C

Material                                                                                                                                                  SS304L

Plate thickness                                                                                                                                     1.6 mm

Plate size                                                                                                                                         2,413 × 565 mm

Number of plates                                                                                                                                  4

Flow arrangement                                                                                                                            2 passes / plate

Heat transfer                                                                                                                                    Double-sided

The above design is based on the customer's application and drawing requirements.

Why Use a Pillow Plate Coil Bank for Alkaline Liquids?

1. Direct Immersion Heating

The Pillow Plate Coil Bank is immersed directly into the process tank.

Instead of transferring heat through a separate external heat exchanger and circulating the alkaline liquid, heat can be transferred 

directly from the coil surface to the surrounding liquid.

This can simplify the overall heating system and reduce the amount of external piping and auxiliary equipment.

2. Large Heat Transfer Surface in a Compact Configuration

Pillow Plates provide a large effective heat transfer surface within a relatively compact volume.

In this project, the total heat transfer area is 10.91 m², with double-sided heat transfer.

The coil bank configuration also allows the heat transfer surface to be arranged according to the geometry of the process tank.

3. Fully Welded Construction

Pillow Plate technology uses welded stainless-steel plates to form the internal flow channels.

For applications involving alkaline process liquids, material selection and weld integrity are critical considerations.

The coil bank in this application is manufactured from SS304L, with a single plate thickness of 1.6 mm.

4. Designed for Pressurized Steam

The coil bank uses steam as the heating medium. The calculated operating condition includes a steam inlet temperature of 150°C 

and a working pressure of 375 kPa(g). The design pressure is 1,300 kPa(g) and the design temperature is 200°C.

This provides an adequate design margin for the specified operating conditions.

5. Suitable for Tank Heating Applications

The immersed Pillow Plate configuration can be considered for various industrial tank-heating applications where a liquid needs to

 be heated or maintained at a stable temperature.

Potential applications include:

﹡Alkaline and chemical process tanks

﹡Cleaning and washing tanks

﹡Surface treatment processes

﹡Food and beverage process tanks

﹡Pickling and chemical treatment systems

﹡Industrial hot-water tanks

﹡Process liquid temperature control

Actual material selection should always be based on the chemical composition, concentration and operating temperature of the 

process liquid.

Pressure Drop and Testing

For the steam side, the calculated pressure drop of the Pillow Plate coil bank is 11.52 kPa(g). The equipment was specified with a

 hydrostatic test pressure of 1,700 kPa, using water as the test medium.

These parameters are important when integrating the coil bank into a pressurized steam system.

From Heat Exchanger to Immersed Heat Transfer Surface

One of the advantages of Pillow Plate technology is its flexibility in configuration.

Rather than limiting the equipment to a conventional shell-and-tube or plate heat exchanger arrangement, Pillow Plates can be 

fabricated into different forms, including coil banks, panels and immersed heat-transfer assemblies.

For tank heating, this means the heat transfer surface can be positioned directly where heat is required.

Steam in → Pillow Plate Coil Bank → Direct heat transfer → Alkaline liquid

This approach can provide a compact solution for industrial heating processes while simplifying the heat-transfer path.

Conclusion

This application demonstrates how a Pillow Plate Coil Bank can be used as an immersed heat-transfer solution for heating alkaline 

liquids.

With its welded construction, compact configuration, double-sided heat transfer and flexible geometry, Pillow Plate technology offers

 an alternative approach to conventional external heat exchangers for industrial tank-heating applications.

For applications involving corrosive or chemically active liquids, the correct material must be selected based on the actual process

 chemistry and operating conditions.

ZZ Thermal develops customized Pillow Plate Heat Exchangers and Coil Banks according to process conditions, tank dimensions 

and heat-transfer requirements.

If you have an industrial tank heating or process heating application, we can evaluate the required heat transfer area, configuration,

 material and operating parameters for your project.