Heat Recovery with Pillow Plates Heat Exchangers
In recent years, there has been a growing interest in pillow plate heat exchangers (PPHEs) because of their versatility to cover a large number of applications in most industries, as well as their high heat transfer efficiency. In our last article of this series, we will present a comparison, on different aspects, between a PPHE and Shell and Tube, Gasketed Plate, and Spiral Heat Exchangers. We will also discuss in particular the use of PPHE applied to high-temperature flue gas energy recovery.
Table 1 shows this comparison for the operating conditions at temperature and pressure, the heat transfer coefficient when using water, the weight of the unit area, and whether or not they can be used to different applications.
Table 1: Comparison between PPHE and Shell and Tube, Gasketed Heat and Spiral Heat Exchanger
Font: Pillow Plate Heat Exchanger” Boucheng.com
It is evident from Table 1 that PPHE is the most flexible heat exchanger among those presented which is suitable for all given applications and can operate in a wide temperature range. In addition to this, a PPHE unit surface has the lowest weight, has the second-highest water heat transfer coefficient, and the second-highest operating maximum pressure range only behind GPHE and STHE respectively.
Vocciante and Kening (2021) confirm the above characteristics presented in Table 1 when they indicate in their research how PPHEs combine the advantages of the most commonly used types of conventional heat exchangers, being pressure and temperature resistant like shell and tube heat exchangers and cost-effective and compact like plate heat exchangers. Furthermore, Vocciante and Kening (2021) highlight the fact that the heat transfer surface area tends to be further reduced compared to other types of plate heat exchangers under the same application conditions, which translates into further advantages in terms of process sustainability.
In the new global economy, thermal heat recovery in industrial processes has become a key factor in reducing environmental impact, energy consumption, and, consequently, costs. There are important applications found in high-temperature flue gas energy recovery such as flue-gas-water heat exchanger, steam-air heat exchanger, flue-gas-air heat exchanger, and steam-water heat exchanger. These applications can be used in a variety of industries including the chemical industry, paper processing industry, food processing industry, wood processing industry, etc.
Many of these applications are already built with pillow plate heat exchangers, taking advantage of their flexibility, temperature and pressure operating conditions, production costs, and high thermal efficiency which helps to lower the life cycle cost of the system.
When making a comparison between two heat recovery applications, one with a PPHE and the other with another type of exchanger, there are two essential factors to evaluate immediately: the amount of energy recovered and the payback period of the application. Other factors such as the amount of CO2 recovered, the size of the unit, and the initial costs are also important to evaluate.
Unilab Srl will soon launch a tool, embedded in our renewed Pillow Suite, that allows the user to evaluate PPHE and do this kind of analysis with practicality, considering many factors such as the cost and weight of the material, the commercial factor, the energy cost, the hours of operation per day, and the days of operation in a year, in order to obtain the annual thermal energy recovered and the annual savings.
Milena Vilar França
Dsc degree in Mechanical Engineering
Engineering Dept., Unilab Srl
References
- Vocciante M., Kenig E.Y., 2021, Pillow-Plate Heat Exchangers: an Overview on Advances, Limitations and Prospects, Chemical Engineering Transactions, 88, 865-870 DOI:10.3303/CET2188144
- “Pillow Plate Heat Exchanger” Boucheng.com boucheng.com/pillow-plate-heat-exchanger-p00023p1.html(accessed November 2021)
