heat exchanger

 

A heat exchanger is an equipment designed to transfer energy from one stream to another through different systems including air, exhaust gases, water, overheated water, refrigerants sludges and steam.

Some of these elements may have demanding characteristics such as viscosities and sediments, in addition to working in corrosive environments.

Some of the main types are:

  • Plates
  • Fins and tubes or finned tubes
  • Smooth tubes
  • Cross flow
  • Coils

In this sense, Boixac Tech offers tailor-made solutions, analyzed in detail, and offering a huge range of heat exchangers for different industries and applications such as wastewater treatment plants, paper mills, power plants, offshores, chemical industries or food processing plants.

Pillow plate for fermentation and thermal control in wineries and breweries

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Pillow plate heat exchangers in breweries and wineries: fermentation cooling and tank temperature control | BOIXAC Technical blog · Food industry › Breweries and wineries Pillow plate heat exchangers in breweries and wineries: fermentation cooling and tank thermal control Why dimple plate technology outperforms conventional jackets for fermentation tank cooling: heat transfer coefficient analysis, CIP cleaning and design criteria for beer and wine production. BOIXAC · Technical OfficeUpdated: 2026Reading: ~11 min Note on the scope of this article This article is of a general technical and informational nature. Heat transfer coefficient values, temperature ranges and design criteria given are indicative; the definitive sizing of a pillow plate heat exchanger for a specific application requires analysis of the actual process conditions by qualified engineers. BOIXAC assumes no liability for decisions taken on the basis of this article. Temperature control during fermentation is one of the technical parameters with the greatest influence on the organoleptic profile of the final product in breweries and wineries. The difference between a fermentation proceeding at 12 °C and one that peaks at 18 °C may be the difference between a clean product and one with undesirable ester and fusel alcohol profiles. Pillow plate technology — also known as dimple plate — has progressively replaced half-pipe jackets and conventional annular jackets on next-generation stainless steel fermentation vessels, thanks to thermal, hygienic and constructional advantages that become especially evident in tank volumes exceeding 5,000 litres. 1. Operating principle of the pillow plate (dimple plate) A pillow plate is a heat exchanger formed by two stainless steel sheets joined at their perimeter and by a regular matrix of resistance spot welds, creating an internal labyrinthine cavity with a very narrow cross-section. When a refrigerant fluid (typically aqueous glycol) circulates through this cavity, the dimple geometry induces local turbulent flow — even at low volumetric flow rates — maximising the internal convection coefficient. The outer sheet of the pillow plate is welded directly to the surface of the fermentation vessel, so that the tank wall simultaneously serves as the load-bearing structure and the heat transfer surface. The embossed geometry of the dimples distributes the refrigerant pressure uniformly across the entire plate surface, allowing operation at relatively high internal pressures (up to 10–15 bar depending on design and sheet thickness) with minimal material thickness. 2. Technical comparison: pillow plate vs. conventional jackets Parameter Pillow plate (dimple plate) Half-pipe jacket Conventional annular jacket Internal convective coefficient (hi) High: dimple geometry induces local turbulence. Typical values: 3,000–8,000 W/m²·K. Moderate-high: tubular flow. 2,000–5,000 W/m²·K. Low-moderate: wide annular flow, often laminar. 500–2,000 W/m²·K. Cooling distribution across tank surface Excellent: continuous, uniform coverage of all covered surface. Good along the pipe length; zones between pipes lack direct contact. Variable: risk of dead zones in large-section annular circuit. Refrigerant fluid volume in circuit Very low: narrow flow passage (typically 3–6 mm). Reduced glycol volume in circuit. Moderate. High: large annular cross-section. Thermal response time Very fast: low fluid volume, reduced thermal inertia. Rapid control system response. Fast-moderate. Slow: large fluid volume, high thermal inertia. Slow response to setpoint changes. Cleanability — product side Excellent: smooth external surface in contact with product, suitable for CIP cleaning. Good. Good. 3. Specific applications in breweries and wineries 3.1. Fermentation vessel cooling in brewing In bottom-fermentation (lager) beer production, temperature control is especially critical because the yeast working window (typically 8–14 °C for standard lager strains) is narrow and the heat generated by alcoholic fermentation is significant: approximately 2.3 kJ are released per gram of fermented sugar. In a 50-hl fermenter with 12 °P wort, the cooling duty required at peak fermentation activity can be between 3 and 8 kW depending on the fermentation rate. Pillow plates welded to the cylindrical tank wall (and, in some designs, to the cone) allow this heat extraction to be distributed homogeneously, avoiding radial temperature gradients that could create localised sub-cooling zones where yeast activity is inhibited or premature precipitation occurs. The fast response of the system — due to the low refrigerant circuit volume — facilitates the use of PID control systems that maintain temperature setpoints within ±0.5 °C, difficult to achieve with high-inertia conventional jackets. 3.2. Must temperature control in wine fermentation In white and rosé winemaking, fermentation temperature control (typically between 12 and 18 °C) is critical for preserving volatile varietal aromas that are lost through volatilisation if temperatures are exceeded. Pillow plates on AISI 304 or 316L stainless steel tanks allow low fermentation temperatures to be reached and maintained with modest refrigeration systems. The ability to reach temperatures close to 0 °C uniformly and in a controlled manner — the so-called cold tartrate stabilisation — is an application that highlights the thermal performance of pillow plate technology over less efficient alternatives. 3.3. Craft breweries and microbreweries In craft breweries with smaller fermenters (100–2,000 litres), pillow plate technology offers additional advantages due to its compatibility with relatively small glycol systems and the ease of integration on cylindroconical stainless steel tanks. The typical configuration consists of one or two independent pillow plate zones (cylindrical and conical sections) connected to a glycol circuit with independent zone control valves, allowing programmable temperature profiles throughout fermentation. 4. Pillow plate sizing criteria for fermentation vessels Peak fermentation thermal duty (Qmax): estimated from fermentation rate, wort concentration (°P or °Brix) and tank volume. In beer production, indicative reference values range from 50 to 150 W per hl of fermenter capacity at peak activity, depending on the recipe and yeast used. Available temperature differential (ΔT): difference between fermenting product temperature and refrigerant inlet temperature to the plate. Minimum refrigerant temperature: in aqueous glycol circuits, glycol temperatures of -2 to -5 °C are generally sufficient for most standard fermentation applications; lower temperatures are used for tartrate stabilisation. Tank surface coverage: the proportion of the total tank surface covered with pillow plate (typically 40–70 % of the lateral surface) must be sufficient to ensure cooling uniformity and avoid vertical temperature gradients in the product. Refrigerant circuit working pressure: pillow plate … Read more

Pressure Equipment Directive PED 2014/68/UE

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Directive 2014/68/EU (PED): regulatory framework for pressure equipment | BOIXAC Technical blog › Regulations & certification Directive 2014/68/EU (PED):the regulatory framework for pressure equipment in the EU A technical guide to the scope of application, risk category classification and conformity assessment modules established by the Pressure Equipment Directive. BOIXAC Tech SL Updated: 2026 Reading time: ~8 min Note on the scope of this article This text is exclusively informational and educational in nature. It does not constitute legal, technical or engineering advice, and cannot under any circumstances replace the specific analysis carried out by a qualified professional on a particular piece of equipment. The correct application of Directive 2014/68/EU — including equipment classification, determination of the assessment module and obtaining CE marking — always requires the involvement of competent engineers and, for higher categories, a duly notified Notified Body. BOIXAC assumes no liability arising from decisions made based on the content of this article. Directive 2014/68/EU of the European Parliament and of the Council, of 15 May 2014, on the harmonisation of the laws of Member States relating to the making available on the market of pressure equipment — commonly known as the Pressure Equipment Directive or PED — is the European regulatory instrument governing the design, manufacture and conformity assessment of pressure equipment intended for the internal market. For any manufacturer or industrial user of pressure equipment — heat exchangers, vessels, boilers, process pipework and fittings — understanding the scope and logic of this Directive is a prerequisite for operating safely and in legal compliance within the European Economic Area. 1. Background and regulatory context Directive 2014/68/EU repealed and recast the previous Directive 97/23/EC, which ceased to apply on 19 July 2016. The recast did not substantially modify the essential safety requirements or the conformity assessment tables, but aligned the legislation with the New Legislative Framework (NLF) of the European Union — in particular Regulation (EU) No 765/2008 and Decision 768/2008 — introducing explicit obligations for all economic operators in the supply chain: manufacturers, authorised representatives, importers and distributors. Key regulatory reference Directive 2014/68/EU of the European Parliament and of the Council, of 15 May 2014 (OJ L 189, 27 June 2014, pp. 164–259). Full entry into force: 19 July 2016. 2. Scope of application The Directive applies to the design, manufacture and conformity assessment of pressure equipment and assemblies with a maximum allowable pressure (PS) greater than 0.5 bar gauge. Element Description under the Directive Vessels Housings designed and built to contain fluids under pressure, including shell-and-tube heat exchangers. Piping Piping components intended for the transport of fluids, including pipes, piping systems, fittings, expansion joints and hoses. Safety accessories Devices protecting against the exceedance of allowable limits: safety valves, pressure relief devices, automatic control systems, etc. Pressure accessories Devices with an operational function subject to pressure: non-return valves, regulators, steam traps, filters, etc. Assemblies Several items of pressure equipment assembled by a manufacturer to constitute an integrated functional installation. Notable exclusions The Directive expressly excludes from its scope, among others: simple pressure vessels covered by Directive 2014/29/EU; aerosol generators; equipment intended for vehicle operation; certain water distribution networks; nuclear equipment; and well-control equipment for the extractive industry. 3. Fluid classification and its significance One of the Directive’s central pillars is the classification of the fluids contained in the equipment, which determines — together with the pressure and volume or nominal diameter parameters — the applicable risk category. Directive 2014/68/EU updated the classification relative to the previous legislation, aligning it with Regulation (EC) No 1272/2008 (CLP) on classification, labelling and packaging of substances and mixtures. Group Fluids included (simplified criterion) Group 1 Fluids considered hazardous: explosive, extremely or highly flammable, toxic, very toxic, oxidising and corrosive under the CLP Regulation, as well as any fluid at a maximum allowable temperature (TS) above its flash point. Group 2 All fluids not included in Group 1, commonly referred to as “non-hazardous fluids”. Key technical consideration The Directive establishes that thermal oils are classified as Group 1 when the maximum allowable temperature of the equipment exceeds the flash point of the oil in question, regardless of its CLP classification. This specific criterion, set out in Commission Guideline B-41, has direct implications for the resulting category of the equipment. 4. Risk categories The Directive establishes four risk categories (I to IV) for pressure equipment. Category assignment is determined using the tables in Annex II, which cross-reference fluid parameters with equipment parameters (PS, volume V or nominal diameter DN). Category IMinimal risk Low-pressure or small-volume equipment. The manufacturer may self-certify via Module A (internal production control). Category IILow risk Requires involvement of a Notified Body in the production phase. Available modules: A2, D1, E1. Category IIIModerate risk Notified Body involvement in design and/or production. Modules: B+D, B+F, B+E, B1+D, G, H. Category IVHigh risk Maximum requirements. Notified Body required at all stages. Permitted modules: B+D, B+F, G, H1. 5. Conformity assessment modules Module Name NB required Summary A Internal production control No Manufacturer’s self-declaration. Applicable to Category I only. A2 Internal production control with supervised checks Yes The NB performs random inspections of the finished product. B EU-type examination (production type) Yes The NB examines a representative specimen. Must be combined with a production-phase module (D, E or F). B1 EU-type examination (design type) Yes The NB examines the design technical documentation without a physical prototype. D / D1 Production quality assurance Yes The NB approves and supervises the manufacturer’s quality system in the production phase. E / E1 Product quality assurance Yes The NB approves and supervises the quality system for final inspections and testing. F Product verification Yes The NB verifies each produced unit by examination and testing. G Unit verification Yes Individual assessment of each item by the NB, both in design and production. Common for one-off equipment. H / H1 Full quality assurance Yes The NB approves and supervises the complete quality management system. H1 adds design examination and special surveillance. 6. Economic operator obligations Manufacturer Ensure the equipment … Read more

Select the materials of a heat exchanger

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Heat Exchanger Material Selection: Chemical Compatibility Guide | BOIXAC Technical guide › Material selection Heat Exchanger Material Selection: Chemical Compatibility by Industrial Application Technical reference guide to support material selection for heat exchangers based on process fluid, industrial sector and operating conditions. From AISI 304/316 stainless steel to Hastelloy, titanium and cupronickel. BOIXAC Tech SL Updated: 2026 Reading time: ~8 min Note on the scope of this guide The information on this page is intended as orientation and general reference only. Material chemical compatibility depends on multiple variables — temperature, pressure, concentration, presence of contaminants, thermal cycling — that cannot be comprehensively captured in a general reference table. The data presented is based on specialist technical literature and BOIXAC’s practical project experience, but does not in any way constitute an engineering specification for a given application. Final material selection validation must always be carried out by a qualified specialist. BOIXAC assumes no liability for decisions made exclusively on the basis of this guide. Material selection is the engineering decision with the greatest impact on a heat exchanger’s lifecycle cost and reliability. An inappropriate material leads to accelerated corrosion, process contamination or premature failure; an over-specified material drives unnecessary cost. This guide provides a structured starting point for engineering, procurement and technical management teams. 1. Standard materials: application range and key characteristics Industrial heat exchangers are typically manufactured in a spectrum of materials covering the majority of process applications. Each presents a distinct profile of chemical, mechanical and thermal resistance. Copper Cu Excellent thermal conductivity. Suitable for non-oxidising fluids, oils and gases. Sensitive to ammonia and oxidising acids. Aluminium Al Lightweight, good conductor. Used in HVAC, automotive and food. Limited in strong alkaline and chloride environments. Carbon Steel CS Robust and cost-effective for general steam, hot gas and non-aggressive oil applications. SS 304 AISI 304 Versatile in food, beverage and light chemical duties. Lower chloride resistance than 316. SS 316 AISI 316 Benchmark for chemical and marine environments. Mo addition improves crevice corrosion and chloride resistance. Hastelloy C-276 / B-3 Maximum resistance in highly corrosive environments: oxidising and reducing acids, mixed media. Titanium Ti Gr. 2 Outstanding in seawater, nitric acid, chlorides and oxidising media. Low density. Cupronickel Cu-Ni 90/10 Reference material for marine and desalination applications. Notable biofouling resistance. Specialist materials for demanding applications For the most demanding environments — concentrated chlorides, strongly oxidising media, extreme temperatures or pharmaceutical hygiene requirements — BOIXAC provides heat exchangers in Hastelloy C-276 and B-3, titanium Gr. 2, cupronickel 90/10, AISI 309 and AISI 310. These materials deliver solutions where standard stainless steels cannot meet the required performance. 2. Key factors determining compatibility A material’s chemical resistance is not a fixed value: it is a function of several variables interacting simultaneously in the real process. Any extrapolation beyond the documented conditions range requires specific validation. Temperature: Corrosion accelerates exponentially with temperature. A material compatible at 20 °C may be unsuitable at 80 °C for the same fluid. Fluid concentration: Acids and bases exhibit non-linear behaviour. Stainless steel, for instance, resists high concentrations of nitric acid but not intermediate ones. Chloride content: Pitting and crevice corrosion in stainless steels is particularly sensitive to Cl⁻ concentration and temperature. Fluid velocity: Erosion-corrosion and cavitation are velocity-dependent. Copper, for example, has velocity limitations in seawater service. pH and redox potential: These determine the passivation or active attack zone on the material’s Pourbaix diagram. Contaminants and trace impurities: Unexpected compounds (sulphides, oxidants, metal ions) can drastically alter material behaviour even at trace concentrations. 3. Compatibility table by fluid and sector The table covers the most common process fluids and compounds across the main industries using industrial heat exchangers, indicating materials for which documented compatibility exists under representative conditions. Empty cells indicate absence of standard-condition compatibility data, not necessarily incompatibility. How to read this table — limitations Compatibility marks (✓) indicate general suitability documented in technical literature under moderate temperature, pressure and concentration conditions. They do not guarantee compatibility under all process conditions. Definitive validation requires reference to ASTM G31, specialist corrosion databases, and where applications are critical, laboratory or pilot testing. Always consult our technical team before finalising a specification. Sector Typical application Fluid / Compound Copper Aluminium CS AISI 304 AISI 316 Notes Food Baking, margarine, hospitality Wheat oil ✓ ✓ ✓ ✓ Energy Machinery, engines Lubricating oil ✓ ✓ ✓ ✓ ✓ Beverages Soft drinks, perfumery Amyl acetate ✓ ✓ Textile Dyeing, perfumery Ethyl acetate ✓ ✓ ✓ ✓ Plastics / Pharma Plastic, fibre, pharmaceuticals Acetone ✓ ✓ ✓ ✓ ✓ Plastics / Textile Pharma, dyes, additives Acetic acid ✓ Conc. <20%. Validate temp. Chemical Pharma, chemical Hydrobromic acid ✓ ✓ Consider Hastelloy Food / Beverage Carbonated drinks, confectionery Citric acid ✓ ✓ ✓ Food Palm oil substitute Stearic acid ✓ ✓ Textile / Paper Dyeing, paper, leather Formic acid ✓ ✓ Avoid Cu and Al Chemical Water treatment Phosphoric acid ✓ ✓ Concentration & temp. dependent Agriculture Fertilisers, metals Nitric acid ✓ ✓ Titanium for high conc. Food / Beverage Olive oil, cocoa Oleic acid ✓ ✓ ✓ Chemical / Petrochem. Fertilisers, refined petroleum Sulphuric acid ✓ High conc. only. Hastelloy recommended Beverages Wine & viticulture Tannic acid ✓ Food / Beverage Baking, gelatine, desserts Tartaric acid ✓ ✓ ✓ Marine Vessels, offshore plants Seawater Cupronickel: reference material Textile Fertiliser, dyeing, cleaning Ammonia ✓ ✓ Avoid copper and Cu alloys Plastics / Textile Plastic, pharma, dye, perfume Acetic anhydride ✓ Validate with stabilisers Chemical Resin, herbicide, varnish Aniline ✓ ✓ Chemical Rubber, lubricant, detergent Benzene ✓ ✓ ✓ ✓ ✓ Beverages Brewing industry Beer ✓ ✓ ✓ Beverages Butter, yoghurt, dairy Milk ✓ ✓ Food Butter, yoghurt, dairy Lactic acid ✓ ✓ 316 preferred >5% Oil & Gas Petrochemical by-products Crude oil ✓ ✓ Titanium: premium option Energy Heating and power Natural gas ✓ ✓ ✓ ✓ Agriculture Fertiliser, hydroponics Potassium sulphate ✓ ✓ Chemical Ink, dye, varnish Resin ✓ ✓ Food Dietary supplements Cereals ✓ ✓ Food Dietary supplements Pickling brine / Vinegar ✓ ✓ 316 for more acidic … Read more