What is Direct Steam Injection Heating?

Direct steam injection (DSI) heating is a highly efficient method of heating liquids and slurries by directly injecting steam into the process fluid. This technique ensures rapid and uniform heating, making it ideal for various industrial applications.

How DSI Works

Direct steam injection heats water or other process liquids by injecting steam directly into the flowing liquid. As the steam condenses, all its energy, both sensible and latent heat, is transferred instantly into the liquid, raising the temperature rapidly and uniformly.

This differs from indirect heating methods, such as heat exchangers or steam coils, where heat must pass through a heat transfer surface. Indirect systems often struggle to maintain tight temperature control under changing flow or demand conditions.

With DSI, heating occurs on a continuous, straight‑through basis—there is no need to store large volumes of hot water, and heating stops immediately when demand stops.

How a Pick Heater Works

Pick Direct Steam Injection Heating Systems can be used to heat any water-miscible liquid or aqueous slurry instantaneously where steam pressure is greater than the liquid-side pressure. 

To heat the process liquids, steam is dispersed through the precisely arranged orifices in many fine streams promoting rapid mixing and instantaneous heat transfer.  As the steam enters the internal injection tube, it acts against a spring-loaded piston to expose some or all the orifice pattern.  As the steam input varies due to load changes, the piston modulates to adjust the number of exposed orifices providing rapid response to process changes. 

The spring and piston arrangement prevents equalization of steam & liquid pressures thus eliminating harmful shock and vibration caused by steam hammer. The helical flights inside the chamber ensure complete and thorough mixing of steam and liquid. 

With a Pick Heater, there are no minimum up or down-stream pipe length requirements.  All steam is smoothly condensed within the mixing body.  Liquid pressure drop is typically only 1 PSI, and the sound level is usually 85 dBA or less.  This is an important contrast to high-velocity or venturi type DSI units. 

Key Features

• 100% Heat Transfer: All the energy from the steam is transferred to the process fluid, making the system highly efficient.
• No Condensate Recovery: Unlike indirect heating methods, there is no need for condensate recovery systems.  The steam condenses and becomes part of the process fluid.

Advantages

• Energy Efficiency: DSI heating systems are known for their high energy efficiency, often resulting in significant fuel savings compared to traditional heat exchangers.  For plants focused on reducing energy consumption and operating costs, this efficiency advantage can be significant.
• Precise Temperature Control: Steam injection systems are designed to maintain tight temperature tolerances, even when subject to variable flow rates or fluctuating inlet water temperatures. Temperature is measured at the outlet and automatically adjusted in real time, helping prevent overheating, wasted energy, or inconsistent results.
  
  This level of control is especially important in sanitary processes, chemical reactions, and applications where repeatability is critical.
• Compact Design: Direct steam injection systems are far more compact than indirect heat exchangers or large storage tanks. Many systems can be wall mounted or installed on a small skid, making them ideal for retrofits or facilities with limited space.

Applications

DSI heating is widely used in industries such as food processing, chemical manufacturing, pharmaceuticals, and pulp and paper. It is particularly beneficial in applications where rapid and uniform heating is essential.
Ready to improve your process heating performance?

Talk with a Pick Heaters expert to see how direct steam injection can deliver faster response, tighter temperature control, and reliable hot water on demand for your operation. Contact us today to get started.