A Brief Introduction to Pillow-Plate Heat Exchangers

Pillow-Plates Heat Exchangers (PPHE) are classified as innovative heat exchangers and are used today in a large range of applications such as ice machines, heat pumps, column reboilers, latent heat storage systems, waste heat recovery, jacketed tanks, etc. They are gaining attention in the industry because of their low-cost production and good thermo-hydraulic performance besides the fact that they have a pressure-resistant construction.

Their principal characteristic is a three-dimensional wavy surface plate, from which the term “pillow” is derived. Figure 1 shows the wavy aspect of a pillow-plate. Another characteristic of the PPHE is that the pillow plates have a low specific weight which is an attribute that allows them to be connected into head sections of distillation columns, for example.

Figure 1. A pillow-plate structure

PPHE have a pressure resistant-construction that offers low-pressure loss and a high heat transfer coefficient. Several numbers of pillow-plates settled as a stack side by side compose this type of heat exchanger. They are equipped with an inlet distributor and an outlet collector for the fluid inside the channels. The plates are formed by two metal sheets settled on one another by spot-welding by laser o resistance methods, as can be seen in Figure 1.

Regarding the plates fabrication process, after they have been welded, they pass through a hydroforming process that inflates them with pressures normally from 60 to 80 bar which are much higher than the operating pressures. The channels formed by this process are separated hermetically and fixed without gaskets.

Commonly plates are made with the same thickness thus when the hydroforming process is applied, both plates deform equally. If the PPHE is composed of plates with different thicknesses, only the thinner deforms, resulting in a one-side expansion. Depending on the thickness plates several models of plates can be obtained as can be observed in Figure 2.

Figure 2. Representation of different Pillow Plates types.
Behrend (1993, apud J. M. Tran et al. 2018, p. 237)

This was our very short introduction about pillow-plates heat exchangers. Below in Figure 3, can be observed some of the applications we have mentioned here. In the next posts, we will explain further about this subject!

Figure 3. Examples of PPHE applications: Ice Macchine (www.thermolazer.com) and Jacketed Tanks (https://www.hanputech.com)

References

• Piper, M., Zibart, A., Tran, J. M., Kenig, E. Y., “A numerical study on turbulent single-phase flow and heat transfer in pillow plates”, Proceedings of the 15th International Heat Transfer Conference, IHTC-15 August 10-15, 2014, Kyoto, Japan, (2014)
• Tran J.M., Piper M., Kenig E.Y., Scholl S. (2018) Pillow-Plate Heat Exchangers: Fundamental Characteristics. In: Bart HJ., Scholl S. (eds) Innovative Heat Exchangers. Springer, Cham. https://doi.org/10.1007/978-3-319-71641-1_7
• “Products. Pillow Plate” Hanputech.com
  https://www.hanputech.com/dimple-plate/pillow-plate.html (accessed November 03, 2021)
• “Urunler” Thermolazere.com
  http://www.thermolazer.com/urunler/#iLightbox[feature]/4  (accessed November 03, 2021)