Type III Detachable Horizontal Spiral Plate Heat Exchanger

Structural Features

1. 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 crucial to reasonably select the channel width and fluid velocity. During design, it is generally advisable to choose higher velocities (approximately 2 m/s for liquids and 20 m/s for gases, within allowable design limits). This allows for higher fluid dispersion and better contact, which is beneficial for enhancing the heat transfer efficiency of the spiral plate heat exchangers. In recent years, many domestic units have conducted heat transfer coefficient comparisons between spiral plate and tubular heat exchangers. For instance, 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 resulted in a doubling of efficiency. Similarly, in the heater below an ammonia synthesis tower, originally using a tubular structure with a heat exchange area of F=30.9 m², switching to a Type III removable spiral plate heat exchanger with only F=15.5 m² doubled the efficiency accordingly.

       2. Can effectively utilize the pressure head loss of fluids

       In the III-type removable spiral plate heat exchanger, although there are no sharp changes in flow direction or pulsations, the fluid resistance is generally higher than that of a shell-and-tube heat exchanger due to the longer spiral channels and fixed-distance columns welded to the spiral plates. However, compared to other types of heat exchangers, the fluid resistance in this design primarily occurs due to 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 spiral plate heat exchanger to effectively utilize the fluid pressure head loss.

       3. Resistant to clogging

       In recent years, numerous studies have focused on the fouling issue of heat exchangers, as fouling significantly affects their heat transfer efficiency. In Type III removable spiral plate heat exchangers, since the medium flows through a single channel, and the permissible velocity can be higher than that of other types, fouling is less likely to accumulate. If fouling deposits in a channel, the cross-sectional area of that section decreases, and under a certain flow rate, a lower cross-sectional area results in higher local flow velocity, which cleans the fouled area. In shell-and-tube heat exchangers, if fouling accumulates in a heat exchange tube, the local resistance increases, restricting flow and reducing velocity, causing the medium to分流 to other tubes. This rebalances the resistance in each tube within the heat exchanger, making the flow velocity of the fouled tube progressively lower, easier to accumulate fouling, and eventually leading to complete blockage. In chemical and oil refineries, shell-and-tube heat exchangers often experience fouling in the tubes, leading to blockages. However, in Type III removable spiral plate heat exchangers, due to their self-cleaning action, the rate of fouling formation is about 1/10 that of shell-and-tube heat exchangers.

       For blockages, overseas commonly use acid washing or hot water cleaning, while domestically, steam blowing is mostly employed, which is more convenient and efficient than using hot water cleaning.

       4. The ability to utilize low-temperature heat sources and control the outlet temperature is crucial to enhance the heat transfer efficiency of the Type III removable spiral plate heat exchanger. To increase the heat transfer driving force, it is necessary. When both fluids operate in a fully countercurrent manner within the spiral channels, the logarithmic mean temperature difference between the two fluids is significant, which is beneficial for heat transfer. Analyzing from the empirical data adopted in the heat exchanger design, the Type III removable spiral plate heat exchanger allows for a relatively low minimum temperature difference, enabling heat exchange even when the temperature difference between the two fluids is only 3°C. Due to the lower allowable 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, uniformly spiral channels, allowing for even 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, and a heat transfer area per unit volume approximately three times that of a shell-and-tube heat exchanger.

       6. Sealed structure is reliable

       Currently, the used Type III removable spiral plate heat exchanger features sealed ends with welding (non-removable) and end cover clamping (removable). The non-removable type ensures welding quality while preventing internal leakage between the two media. The removable type uses end covers with a full-sealing plate. As long as the two ends of the spiral channels are machined smooth, it can prevent fluid from bypassing from one side to the other.

       7. Small temperature difference stress

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

Technical Specifications