How Heat Exchangers Work During Clean-in-Place

Heat exchangers help control fluid temperatures in processing industries for pasteurization, sterilization, clean-in-place (CIP), and other hygienic operations. In this article, we will highlight how heat exchanges work during CIP operations.

Heating systems for CIP provide temperature control for water and cleaning agents. CIP refers to the equipment and a method for cleaning interior surfaces of pipes, vessels, process equipment, filters, and fittings without disassembly. Industries that rely heavily on CIP include dairy, beverage, brewing, pharmaceutical, biotechnology, and personal care industries to achieve faster, less labor-intensive and more repeatable results than manual cleaning. CIP design also poses less of a chemical exposure risk to operators.

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Clean-in-place systems can operate either in a single pass in which CIP hot water goes to a drain, or a re-circulated system with CIP hot water returning to a central tank system.

In both cases, CIP systems include heat exchangers for heating cleaning fluids to the proper temperature.

Heating in CIP uses two techniques:

  1. Indirect contact of steam via heat exchangers in which heat is transferred from steam across a thermally conducting but an impermeable barrier, such as metal plates
  2. Direct contact of steam with CIP fluids via steam injection

Because of the relatively high cost of direct steam injection and the potential impact of steam on processed fluids, indirect contact plate and frame heat exchangers are typically preferred and much more common than direct steam injection in CIP systems.

Heat Exchanger

Types of Heat Exchangers Used in CIP

Capacity and pressure requirements in CIP systems vary dramatically, and manufacturers have responded to demand with a variety of designs for heat exchangers.

Plate-and-frame Heat Exchanger

Plate-and-Frame Heat Exchangers

With a relatively low steam pressure requirement of around 50 psi, plate and frame heat exchangers are common in CIP systems. High efficiency and modest pricing make them the first choice for many CIP designs.

  • May require a steam reducer to get down to 50 PSI
  • Lower cost
  • Can change duty by adding/removing plates

Shell-and-tube Heat Exchanger

Shell-and-Tube Heat Exchangers

A simple, low maintenance in-line heating option. Common in many CIP systems but may require higher steam pressures and volumes to sufficiently heat solutions quickly.

  • Accommodates higher PSI, so no need for a pressure reducer
  • Higher cost
  • Cannot change duty later

    Alfa Laval AXP Brazes Plate Heat Exchanger

    100% Stainless Steel Plate Heat Exchangers

    Designed for tap and warm water applications to prevent trace nickel and copper leaking, a 100% stainless steel design is well-suited for tap water duties. 100% stainless is a safer alternative to conventional brazed heat exchangers because 100% of stainless designs are not treated with coatings.

    • Minimizes metal release into the environment
    • For heating and cooling
    • Industry-standard port configurations and connections

    How Plate & frame heat exchangers work

    Indirect-contact plate and frame heat exchangers raise or lower fluid temperatures in processing systems using water or steam. “Indirect-contact” design means that the heating or cooling fluid does not mix with CIP fluids. Instead, heat transfers from one fluid to another across a thermally conducting but impermeable barrier, such as a specially designed metal plate. 

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    Heat exchangers feature two alternating fluid flow paths that prevent fluids from mixing. Plate corrugations create turbulence that prevents or reduces fouling by minerals, proteins, and other processed fluids.

    Plate gaskets seal the channels between plates and direct fluids into alternating channels. High-temperature fluids exchange heat with low-temperature fluids through the plates.

    To determine the number of plates in the frame, engineers calculate the heat transfer required based on the system flow rate, physical properties of processed fluids, amount of pressure drop available, and temperature requirements.

    Gasketed plate heat exchangers designed specifically for steam use are suitable for hot water sets in pasteurization and CIP heating.

    They are also suitable for liquid-liquid or liquid-phase change applications if the operating pressures and temperatures are less than about 145 psi and 350°F.

    Direct-contact steam injection for CIP

    Direct-contact steam injection heating in cleaning applications offers: 

    • Precise temperature control
    • Reduced energy consumption
    • Lower maintenance costs than indirect contact via plate and frame heat exchangers. 

    While direct-contact injection provides 100 percent thermal efficiency, their equipment and chemical costs are considerably higher than the cost of indirect-contact methods.

    While initial costs can be higher, direct-contact steam injection does offer some advantages:

    • Installed in line with the CIP piping 
    • Typically more compact than indirect heat exchangers
    • Transfers heat by injecting precisely metered amounts of steam from a plant’s steam supply into the CIP fluid
    • Results in more rapid heat transfer and more efficient energy usage 
    • Energy savings can be considerable — reductions in the 20—25% range are not uncommon
    • Precisely metered injections of steam directly into the cleaning solution are typically quicker and more accurate than other heating options 

    Processing operations must ensure a saturated steam supply, which is the result of steam conditioning to prevent superheated steam or an insufficient steam supply. Steam quality in the food industry must meet “Culinary Steam” requirements and in the biotech industry, specifications for “Clean Steam” must be met. Steam conditioning must take place to maximize heat transfer, and chemicals used in conditioning add to processing costs.

    Steam condensation

    Steam heat exchangers are thermally optimized for steam condensation duties for heating water and for heating clean-in-place (CIP) solution by means of steam and other heating and cooling applications. Operators modify steam heat exchangers by adding or removing plates.

    Understanding Heat modulation

    To optimize cleaning and achieve consistent, reliable results, CIP systems modulate heating to adjust to processing variables. Direct-contact steam heaters can be classified as either: 

    • Externally modulated 
    • Internally modulated

    Which refers to how the steam injected into the CIP fluid is controlled.

    External modulation of heat

    An externally modulated steam heater uses a steam-pressure control valve to regulate the amount of steam injected into the CIP process. The valve is located in the supply steam piping. 

    At times, steam velocity and the volumes of steam and fluid mixing can vary widely over the operating range. Vibration, poor temperature control, and inefficiency result in some operating conditions. Tank spargers, which use external modulation, can experience steam hammer and vibration damage to tanks. Energy inefficiencies also can occur with this heating method when the steam does not completely mix and escapes from the tank.

    Internal modulation of heat

    With the internally modulated direct-steam injection heater, steam flow is controlled through a stem-plug assembly inside the heater. Changing the steam discharge area of the nozzle changes the amount of steam passing through the nozzle and maintains good mixing characteristics.

    Internally modulated direct-contact steam heaters inject metered amounts of steam into the CIP fluid through a variable-area steam nozzle. The nozzle design ensures constant steam pressure and velocity at the point where steam contacts the liquid, eliminating the potential for pressure upsets and ensuring smooth heater operation. 

    Internally modulated direct-steam injection heaters are cleaned by their own turbulent mixing action, usually sonic velocity steam, so they do not encounter fouling or scale buildup.

    Indirect heat modulation with steam

    Plate-and-frame and shell-and-tube designs may use steam instead of hot water to heat fluids indirectly (vs. via direct steam injection). In plate-and-frame steam-heating applications, the fluid to be heated and the steam doing the heating flow through alternating plate channels. In shell-and-tube steam-heating applications, the fluid to be heated flows through the tubes, and the steam circulates in the shell. In both cases, angle seat control valves regulate the amount of steam.

    The valve varies flowrate and steam pressure to control temperature. A sensor monitors actual temperature with target setpoint temperature and signals an actuator to adjust accordingly.

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      Clean-in-place vs Steam-in-place

      For the most part, the CIP process is an entirely automatic one, to comply with specific process requirements. CIP is a series of defined steps using cleaning temperatures of up to 210°F. CIP maintains turbulent flow rates of 5-7ft/s for removing impurities.

      Steam-In-Place is an extension of the CIP process to add sterilization without having to disassemble the processing system and measuring equipment.

      Sterilization of hygienic processes occurs at the end of the CIP process to ensure that microorganisms still active in the system are killed with hot water or steam at high temperatures (> 121 °C).

      Clean-in-place Pharma Skid

      How to Clean a Heat Exchanger

      The Journal of Food Engineering points out that fouling of minerals, proteins onto the surface of heat exchanger plates is a concern for the food industry because of the effects fouling has on heat transfer rates and on overall system efficiency, resulting in increased operating expense.

      Should fouling occur in a heat exchanger, a CIP system enables in-line cleaning without dismantling the equipment. CIP also descales lime deposits, passivates cleaned surfaces to reduce susceptibility to corrosion, and neutralizes cleaning liquids before draining.

      CIP systems connect directly to heat exchangers or via separator connections and circulate a mixture of heated non-toxic cleaning agents that remove scale, product deposits, and biofouling to restore performance.

      Fabricated CIP systems suitable for very large heat exchangers require custom engineering.


      As you've learned, heat exchanger styles can vary widely based on a number of variables, which can make the proper selection for your process appear daunting. We're here to help!

      Whether you need parts to keep your current units operating, a direct replacement for a worn out or inefficient heat exchanger, or a new unit for a new process, CSI can support you.

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