Type III Detachable Horizontal Spiral Plate Heat Exchanger

Structural Features

High thermal efficiency

       Due to the spiral channels of the removable spiral plate heat exchangers of type III, the fluid flows within these channels. Fixed distance columns or stamped distance bubbles are welded to the spiral plates to maintain the width of the spiral channels. Under the centrifugal force of the spiral flow, the fluid can experience turbulence at a lower Reynolds number. Considering that the pressure drop should not be excessive, it is important to reasonably select the channel width and fluid velocity. During design, higher velocities can generally be chosen (with allowable design velocities of about 2 m/s for liquids and about 20 m/s for gases), which allows for higher fluid dispersion and better contact, thereby enhancing the heat transfer efficiency of the spiral plate heat exchangers. In recent years, many domestic units have conducted comparative measurements of the heat transfer coefficients between spiral plate and tubular heat exchangers. For example, in the auxiliary ammonia condenser of a refrigerator, replacing a tubular heat exchanger with a heat exchange area of F=75 m² with a type III removable spiral plate heat exchanger with a heat exchange area of F=30 m² doubled the efficiency. Similarly, in the heater under the ammonia synthesis tower, which originally used a tubular structure with a heat exchange area of F=30.9 m², switching to a type III removable spiral plate heat exchanger with F=15.5 m² also doubled the efficiency.

       2. Can effectively utilize fluid head loss

       In the III-type removable helical plate heat exchanger, although there are no sharp changes in flow direction or pulsation, the fluid resistance is generally higher compared to shell-and-tube heat exchangers due to the longer spiral channels and fixed-distance columns welded to the spiral plates. However, the fluid resistance is primarily caused by friction with the spiral plates and collisions with the fixed-distance columns, which can induce turbulent flow. This results in an increased heat transfer coefficient, allowing the III-type removable helical plate heat exchanger to effectively utilize fluid pressure head loss.

       3. Non-clogging

       In recent years, numerous studies have focused on the issue of fouling in heat exchangers, as fouling significantly impacts their heat transfer efficiency. In Type III removable spiral plate heat exchangers, since the medium flows through a single channel and the allowable velocity is higher than in other types of heat exchangers, fouling is less likely to accumulate. If fouling does settle in a channel, the cross-sectional area of that section decreases, and at a certain flow rate, a reduced cross-sectional area corresponds to an increased local velocity, which acts as a flushing effect on the fouled area. In shell-and-tube heat exchangers, if a heat exchange tube accumulates fouling, the local resistance increases, restricting flow and reducing velocity. The medium then diverts to other tubes, rebalancing the resistance across each tube in the heat exchanger. This causes the velocity in the fouled tube to decrease further, making it easier for fouling to settle and potentially leading to complete blockage. In chemical and oil refineries, the inner diameter of shell-and-tube heat exchangers often experiences fouling, leading to clogging. However, in Type III removable spiral plate heat exchangers, due to their self-cleaning action, the rate of fouling formation is approximately 1/10 that of shell-and-tube heat exchangers.

       For clogging occurrences, abroad, they commonly use acid washing or hot water cleaning, while domestically, the majority opt for steam blowing, which is more convenient and efficient than hot water cleaning.

       4. Utilizes low-temperature heat sources and can control the outlet temperature. To enhance the heat transfer efficiency of the removable spiral plate heat exchanger type III, it is necessary to increase the heat transfer driving force. When both fluids operate in a fully countercurrent manner within the spiral channels, the logarithmic mean temperature difference between the two fluids is greater, which is beneficial for heat transfer. Analyzing from the empirical data used in the heat exchanger design, the removable spiral plate heat exchanger type III allows for a minimum temperature difference that is low, enabling heat exchange even when the temperature difference between the two fluids is 3°C. Due to the lower permissible temperature difference, countries around the world utilize this type of heat exchanger to recover low-temperature thermal energy.

       Type III removable spiral plate heat exchangers feature two longer, evenly spiral channels, allowing for uniform heating and cooling of the medium, thus enabling control over the outlet temperature.

       5. Compact structure

       A 1.5m diameter and 1.8m wide Type III removable spiral plate heat exchanger with a heat transfer area of up to 200m², offering approximately three times the specific heat transfer area of a shell-and-tube heat exchanger.

       6. Sealed structure is reliable

       Currently, the Type III removable spiral plate heat exchanger we use features sealed ends with welding (irreversible) and end cover clamping (removable). The irreversible seal ensures welding quality while preventing internal leakage between the two media. The removable ends are clamped with end covers, which have a full sealing plate. As long as the two ends of the spiral channels are smoothly machined, it can prevent fluid from one side from bypassing to the other side.

       7. Small temperature difference stress

       The III-type removable spiral plate heat exchanger features allow for expansion. Due to its two longer spiral channels, when the spiral plates are heated or cooled, they can extend and contract like a spring inside a clock. Each turn of the spiral has one side for hot fluid and the other for cold fluid, with the outer turns in contact with the atmosphere. The temperature difference between the spirals is not as pronounced as the temperature difference between the tubes and shell in a tube-and-shell heat exchanger, thus preventing significant temperature difference stresses.

Technical Specifications