Comparison of the two types of heat exchangers

Whether a heat exchanger is good or bad depends on the heat exchange process; it cannot be generalized

They should each have their own characteristics and be used in different situations; it’s the main manufacturing process that determines which one to use

Each has its advantages and disadvantages; it depends on the processing conditions

It depends on the occasion of use； Medium, temperature, flow rate, heat transfer amount, comprehensive consideration

Each has its advantages and disadvantages; it cannot be simply compared – one must consider the appropriate situation

It depends on how you use it... but if the difference isn’t significant... the coil-type ones are cheaper

It is selected as required; however, in terms of price, the tube-type version is more expensive than the coiled-type one, and its service life is longer than that of the coiled-type version (under the same operating conditions). Tube-type repairs are more convenient.

The tubular heat exchanger (shell-and-tube heat exchanger) features a compact structure, with a large heat transfer area per unit volume (40–150 m2/m3). It offers excellent heat transfer performance, high adaptability, and great operational flexibility. It is particularly suitable for use in high-temperature, high-pressure environments as well as in large-scale installations, and it is the most commonly used type of tubular heat exchanger. In a shell-and-tube heat exchanger, due to the different temperatures of the fluids inside and outside the tubes, the tube bundle and the shell experience varying degrees of heating, which results in differences in their rates of thermal expansion. If there is a large temperature difference between the two fluids, thermal stress may cause the equipment to deform, the pipes to bend or even break, and in severe cases, they may fall off the pipe sheet. Therefore, when the temperature difference between the two fluids exceeds 50°C, the effect of thermal expansion must be taken into account in terms of design, and appropriate thermal compensation measures should be implemented. A spiral plate heat exchanger is made up of two parallel thin metal plates that are rolled into concentric spiral channels. A partition is placed in the center to separate the two channels, with spacers welded between the two partitions to maintain the distance between the channels; covers and nozzles are welded to both sides of the spiral plates. The two fluids flow in separate channels, exchanging heat through spiral plates. The characteristics of spiral plate heat exchangers are: (1) high overall heat transfer coefficient. Due to the effect of inertial centrifugal force on the fluid within the spiral channels, as well as the interference from the spacer columns, turbulence can be achieved at low Reynolds numbers (Re=1400–1800). This allows for high flow velocities (2 m/s for liquids and 20 m/s for gases), resulting in a high heat transfer coefficient. For the heat exchange process between water and water, K=2000～3000 W/m2·K. ? (2) Resistant to scaling and blockage: Due to the high flow velocity and the flow through the spiral channels, there is a self-cleaning effect, so the suspended particles in the fluid do not tend to settle. ? (3) Ability to utilize low-temperature heat sources: Due to the long flow channels and the complete counterflow between the two fluids, a large temperature difference for heat transfer exists, allowing full utilization of heat sources with lower temperatures. ? (4) Compact structure: Due to the thin plates of 2–4 mm thickness, the heat transfer area per unit volume can reach 150–500 m2/m3. ? The main drawback is that the operating pressure cannot exceed 2 MPa, and the operating temperature must be below 300–400°C. Additionally, since the entire heat exchanger is welded together, it is difficult to repair once damage occurs. Spiral plate heat exchangers have a diameter of up to 1.5 meters, a plate width of 200–1200 mm, a plate thickness of 2–4 mm, and a gap between the plates of 5–25 mm. They can be manufactured from ordinary steel or stainless steel, and are currently widely used in industries such as chemicals, light industry, and food processing.