Type III removable helical plate

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 cloud, the fluid can experience turbulence at a lower Reynolds number. Considering that the pressure drop should not be excessive, the rational selection of channel width and fluid velocity is crucial. During design, it is generally advisable to choose higher velocities (approximately 2m/s for liquids and 20m/s for gases, within the allowable design range). This promotes higher fluid dispersion and better contact, 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, an auxiliary ammonia condenser for refrigeration units, which was originally equipped with a tubular heat exchanger with a heat exchange area of F=75m², was replaced with a type III removable spiral plate heat exchanger with a heat exchange area of F=30m², doubling its efficiency. Similarly, a heater in an ammonia synthesis tower at a small chemical fertilizer factory, originally using a tubular structure with a heat exchange area of F=30.9m², was replaced with a type III removable spiral plate heat exchanger requiring only F=15.5m², also doubling its efficiency.

       2. Can effectively utilize fluid pressure head loss

       In the Type III removable helical plate heat exchanger, although there are no sharp changes in flow direction or pulsations, the fluid resistance is generally higher than that of shell-and-tube heat exchangers due to the longer spiral channels and the welded spacers on the plates. However, compared to other types of heat exchangers, the fluid resistance is primarily caused by friction between the fluid and the spiral plates and impacts with the spacers, which can lead to turbulence. This increases the heat transfer coefficient, allowing the Type III removable helical plate heat exchanger to effectively utilize the pressure head loss of the fluid.

       3. Resistant to 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, due to the single passage for the medium and the higher allowable velocity compared to other types, fouling is less likely to accumulate. If fouling does accumulate in a section of the channel, the cross-sectional area of that section decreases. With a certain flow rate, a reduced cross-sectional area corresponds to an increased local flow velocity, which serves to scour the fouled area. In shell-and-tube heat exchangers, however, if fouling accumulates on a heat exchange tube, the local resistance of that tube increases, restricting flow and lowering velocity. The medium then diverts to other tubes, re-balancing the resistance across each tube in the heat exchanger. This causes the flow velocity in the fouled tube to decrease further, making it more prone to fouling and eventually leading to complete blockage. In chemical and oil refineries, the inside diameter of shell-and-tube heat exchangers often experiences fouling, leading to potential blockages. In contrast, the Type III removable spiral plate heat exchangers, with their self-scouring action, have a fouling formation rate approximately one-tenth that of shell-and-tube heat exchangers.

       For blockages, overseas commonly use acid washing or hot water cleaning, while in China, the majority opt for steam blowing, 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 essential to enhance the heat transfer efficiency of the Type III removable spiral plate heat exchanger. To increase the heat transfer driving force, it is required. When both fluids operate in a fully counter-current mode within the spiral channels, the logarithmic mean temperature difference between the fluids is significant, which is conducive to heat transfer. Analyzing from the empirical data adopted in the heat exchanger design, the Type III removable spiral plate heat exchanger allows for a low minimum temperature difference, enabling heat exchange even when the temperature difference between the two fluids is 3℃. 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 coiled 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, 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 Type III removable spiral plate heat exchanger is equipped with two channels at the ends, featuring welded sealing (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 utilizes end covers with a full sealing plate. As long as the spiral channel end surfaces are machined smooth, it can prevent fluid from bypassing from one side to the other.

       7. Low temperature difference stress

       Type III removable spiral plate heat exchangers feature expansion capability. Due to their two longer spiral channels, they can expand and contract like a clock spring when heated or cooled. Each turn of the spiral is one side for hot fluid and the other for cold fluid, with the outermost turn in contact with the atmosphere. The temperature difference between the spirals is not as pronounced as between the tubes and shell in shell-and-tube heat exchangers, thus avoiding significant temperature difference stress.

Technical Specifications