Conventional Shell and Tube Heat Exchangers have been applied in various industries for centuries. This type of heat exchanger consists of a shell and a bundle of plain tubes inside it. Our Partner Isotherm-Inc is heavily focusing on providing solutions in the heat exchanger industry to increase the thermal efficiency of heat exchangers and especially the shell and tube heat exchanger.
Isotherm-Inc has registered several patents* for the application of enhanced surface tubes to increase the thermal efficiency of the heat exchangers. A plain tube has a smooth surface. Enhanced tubing is a more structured surface which helps facilitate more turbulence and you need turbulent flow for better heat transfer. With very viscous fluids such as propylene glycol, there is high resistance to heat transfer. With enhanced tubing, the turbulence facilitates better heat transfer which enables us to reduce the size of the equipment. It is important to have an enhanced tubing technology to get a compact size heat exchanger.
Aside from the special tube surface feature, the filling beads are applied in this heat exchangers to increase the heat transfer efficiency. The key feature is the presence of small beads filling the spaces between the tubes. These beads help distribute the refrigerant more evenly and improve heat transfer, while also reducing the overall refrigerant charge needed.
The SX® heat exchangers are a low Ammonia Charge Patented heat exchanger which is perfectly suitable for Glycols and Other Viscous Fluids for low temperature applications. It has 2-5 times better thermal performance compared to the conventional shell and Tube heat exchangers. And 50 % less pressure drop penalty. This even beats the plate and frame heat exchanger when it comes to Ammonia Charge.
The following Chart shows a comparison between SX®, Conventional shell and Tube (plain surface), and Plate and frame Evaporator:
| Item / HX models | Conventional shell and Tube | Plate and Frame | SX® |
| Shell Diameter (in) | 48 | NA | 28 |
| Tube Length (ft) | 20 | NA | 16 |
| Separator Diameter (in) | 24 | 42 | NA |
| Separator OAL (ft) | 19 | 10 | NA |
| L (in) x W (in) H (in) | 275 x 54 x 96 | 144 x 54 x 144 | 216 x 34 x 48 |
| Empty Weight (lbs) | 26,500 | 6,600 | 6,100 |
| Pressure Drop (psi) | 18.1 | 14.5 | 9.5 |
| Required Ammonia charge (lbs) | 3558 | 656 | 95 |
Benefits :
- Increased heat transfer
- Lesser refrigerant charge
- Lower Pressure drop
- Smaller equipment
- Saving Material cost
- Saving the available space. This is very essential in Marine Industry
- Lower hazard of refrigerant if there is a leakage. This is very important in case of Ammonia refrigeration due to Ammonia’s Toxicity characteristic.
- Lesser volume leads to a lower PED category of the equipment
Heat Exchangers for Heat Pump Applications in District Heating using Natural Refrigerants
In 2010, Isotherm, Inc. designed and fabricated several high efficiency heat exchangers for a 14 MW District Heating facility in Drammen, Norway. The heat source is cold seawater from the Norwegian fjords, while the refrigerant for this heat pump application is ammonia. More information regarding the Drammen facility has been highlighted in an article published by the British Broadcasting Corporation (BBC); refer to the following link: https://www.bbc.com/news/business-31506073
The list of the heat exchangers built are as follows:
- Titanium Shell & Tube Low Charge Ammonia Spray Chiller (Cooling seawater to 39.2 F with only 3.6 F approach)
- Shell & Tube Stainless Steel Enhanced Tube Sub-cooler
- Shell & Tube Stainless Steel Enhanced Tube Intercooler
- Shell & Tube Stainless Steel Enhanced Tube Desuperheater
- Shell & Tube Stainless Steel Enhanced Tube Condenser
Isotherm’s design of heat exchangers for heat pump applications is not new and is striving to develop its technology for this application in order to contribute the goal of reducing the carbon footprint.
(*) Some of the registered Patents:
- Flooded Evaporator with various kinds of tubes.
- Compressor oil removal in Ammonia refrigeration System.
- Low Charge Refrigeration flooded Evaporator.
- Plate Evaporative condenser and cooler.
- End Bonnets for shell and Tube DX evaporator.
- Distributor for plate heat Exchangers.
Kara Means Efficient and Reliable at Kara Consulting we are proud to offer heat exchangers with the most heat transfer efficiency.
