Developing Innovative Heat Exchangers in a Small-Medium Enterprise: Modelling and Implementation of Pillow Plate Heat Exchangers

The increasing demand for energy-efficient thermal management solutions has driven innovative approaches in heat exchanger design, with Pillow Plate Heat Exchangers (PPHEs) emerging as a promising technology. After a concise but complete overview on the available scientific literature, this research explores the design, experimental validation, and application potential of Pillow Plate Heat Exchangers (PPHE) through a comprehensive investigation conducted within a Small-Medium Enterprise (SME) environment. This study first develops a robust effectiveness-NTU design methodology, adapting established heat transfer principles to the unique geometric characteristics of pillow plates across diverse applications including natural convection, sensible heat transfer, sand cooling, with an only drafted conceptualisation for condensation heat recovery. Within this research work, experimental set ups and prototypes are built for model validation, with a custom-designed Small-Scale Pillow Plate Heat Exchanger (SSPPHE) apparatus revealing critical insights into thermal and hydraulic performance. Tomographic analysis and laser scanning emerged as practical techniques for geometric characterization, identifying significant border effects that explained the consistent 15-30% underestimation of pressure drop by current correlations applied to SSPPHE. Despite these geometric complexities, thermal performance predictions demonstrated acceptable agreement with experimental measurements, with thermal power deviations typically within ±15%. A major achievement was the establishment of a complete 3kW laser welding production facility, enabling rapid prototype development while generating critical manufacturing insights regarding material selection, welding parameters, and quality assurance protocols. This production capability facilitated successful implementation across multiple industrial applications, including natural convection systems for tank heating, a 400kW sand cooling system for foundry applications, and specialized AISI 904L heat exchangers for corrosive diesel exhaust and biomass combustion gases. This section is also a testimony of the Return on Investment of R&D investment in the dynamic and customer focused environment of a SME; the product lines created from the PPHE prototypes went on generating revenues useful for more research endeavours. Preliminary condensation heat recovery experiments demonstrated substantial thermal intensification potential, with latent heat recovery increasing total thermal power by up to 567% compared to sensible-only conditions. When cooling hot waste fumes, or when drying with hot air, great amounts of energy are wasted in the moisture content, and condensation is often avoided due to the corrosion damage it can cause to conventional heat exchanger equipment. PPHE represent a promising alternative, due to their great cleanability, availability of tested corrosion materials and surface treatments. Ultimately, this research establishes a bidirectional knowledge transfer mechanism between theoretical modelling and practical implementation, demonstrating that successful PPHE advancement requires integration of scientific understanding with manufacturing expertise. While identifying several critical areas requiring further investigation, including refined geometric modelling and correlation development, this work provides a foundational framework for both future research and industrial application of this promising heat exchanger technology.