Views: 0 Author: Site Editor Publish Time: 2026-09-23 Origin: Site
A dry cooler (also known as an air-cooled fluid cooler) cools a 50% water / propylene glycol (PG) mixture by circulating the fluid inside sealed, finned-tube coils while axial fans force ambient air across the external finned surface. Because the process fluid is entirely contained within a closed loop, the glycol solution remains free from contamination, evaporation, and water consumption.
However, sizing a dry cooler for 50% propylene glycol by volume requires specific engineering adjustments compared to pure water:
Heat Capacity Derating: 50% propylene glycol has a specific heat (cp≈3.55−3.70 kJ/kg⋅Kcp≈3.55−3.70 kJ/kg⋅K) that is roughly 12% to 15%12% to 15% lower than water, requiring approximately 10% to 18%10% to 18% higher mass flow rates for the same heat duty.
Reduced Heat Transfer Coefficient: The lower thermal conductivity and higher viscosity of 50% PG reduce the inside-tube convective heat transfer coefficient (hihi) by 25% to 35%25% to 35%, requiring a larger coil surface area (typically 15% to 25%15% to 25% more area than a pure water unit).
Higher Fluid Pressure Drop: At typical operating temperatures, the dynamic viscosity of 50% PG is 2.5× to 4.5×2.5× to 4.5× higher than water, increasing tube-side pressure drop by 1.8× to 3.0×1.8× to 3.0× and demanding properly designed multi-pass circuiting and pump selection.
Reliable Freeze Protection: The 50% PG concentration depresses the fluid freezing point to approximately −33∘C to −34∘C−33∘C to −34∘C (−28∘F to −29∘F−28∘F to −29∘F), offering reliable winter burst protection down to below −50∘C−50∘C in cold-climate outdoor installations.
At CSTHEATEXCHANGER, we engineer custom dry coolers, V-bank fluid coolers, and modular air-to-water/glycol heat exchangers specifically calculated for 50% propylene glycol loops, matching tube metallurgy, fin density, circuit passes, and variable-speed fan arrays to your precise flow and temperature targets.
An aqueous solution of 50% propylene glycol and 50% water (by volume) is one of the most widely used secondary coolants in industrial heat rejection, HVAC free cooling, and commercial process systems.
Unlike ethylene glycol (which is toxic and restricted in food, beverage, or environmentally sensitive installations), propylene glycol offers a low-toxicity profile, making it the preferred thermal fluid for:
Data Centers & Edge Computing Facilities: Closed-loop heat rejection in sub-zero winter regions where cooling coils are exposed to freezing ambient air.
Food, Beverage & Brewery Processing: Wort cooling, fermentation vessel temperature control, and dairy cold rooms where non-toxic fluids prevent contamination risks.
Pharmaceutical & Cleanroom Chillers: Reliable process heat dissipation across critical chemical batching processes.
Outdoor HVAC Free-Cooling & Heat Pumps: Winter economizer loops that bypass mechanical chillers to reject heat directly into cold ambient air.
Power Generation & Mining Enclosures: Cooling water-glycol jacket loops for generators, transformers, and immersion computing tanks.
The primary operational purpose of adding 50% propylene glycol is frost and burst prevention. When water freezes, it expands by approximately 9%, rupturing copper or stainless-steel heat exchanger tubes. A 50% PG mixture prevents ice crystallization down to −33∘C−33∘C and transitions into a slushy state without structural expansion down to −50∘C−50∘C, allowing year-round outdoor dry cooler operation.
At CSTHEATEXCHANGER, we specialize in custom thermal engineering for closed-loop air-cooled systems. We do not apply generic "one-size-fits-all" catalogue tables; instead, every unit is calculated based on your exact water-glycol concentration, local climate conditions, and allowable power budgets.
Our Capabilities Include:
Custom Coil Circuiting: Proprietary thermal-hydraulic modeling to balance inside-tube velocity and pressure drop.
Flexible Dimensions & Orientations: Horizontal, V-shape, modular dry coolers, and dual-circuit configurations tailored to restricted rooftop or containerized spaces.
Broad Material Portfolio: Copper, 304/316L stainless steel, titanium tubes; bare, hydrophilic, epoxy, or E-coated aluminum and copper fins.
Complete Pre-Wired Assemblies: Factory-assembled with EC fans, integrated terminal boxes, isolation switches, and optional PLC control panels for plug-and-play field commissioning.
A dry cooler is a closed-loop heat rejection system where a 50% water / propylene glycol mixture flows inside sealed finned tubes while ambient air is forced over the outside surface by axial fans. It cools the fluid without water loss, evaporation, or scaling.
Because 50% propylene glycol has lower specific heat, lower thermal conductivity, and higher viscosity than water, the inside-tube heat transfer coefficient drops by 25%–35%. As a result, a dry cooler for 50% PG typically requires 15% to 25% larger coil surface area and approximately 10% to 18% higher volumetric flow rate than a water cooler of the same kW rating.
A 50% propylene glycol by volume solution freezes at approximately −33.3∘C−33.3∘C (−28∘F−28∘F) and provides burst protection down to below −50∘C−50∘C (−58∘F−58∘F), making it ideal for harsh winter conditions.
Propylene glycol has a dynamic viscosity up to 4.5 times higher than water at room temperature (and even higher at near-freezing temperatures). This increases fluid friction against the tube walls, resulting in a tube-side pressure drop that is 1.8 to 3.5 times higher than pure water at equal velocities.
Adiabatic pre-cooling pads should be added when peak summer ambient dry-bulb temperatures are too high to achieve the required glycol leaving temperature in dry mode. The pads evaporatively cool the incoming air toward the wet-bulb temperature, boosting cooling capacity during extreme heat without wetting the coil tubes directly.
Standard installations typically use seamless copper tubes with hydrophilic aluminum fins. For coastal, chemical, or marine environments, 304/316L stainless steel tubes and epoxy-coated or E-coated aluminum fins provide superior resistance to airborne salt and corrosive vapours.
Yes, but its cooling capacity will be derated by approximately 15% to 25%, and the fluid pressure drop will increase significantly. You must verify that your circulation pump can overcome the higher fluid head and that the reduced heat rejection still meets your process demands.
To select and quote the optimal dry cooler, please provide:
Total heat rejection duty (kWkW or kcal/hkcal/h);
Fluid composition (50% propylene glycol / 50% water);
Fluid inlet and required outlet temperatures (∘C∘C);
Fluid flow rate (m3/hm3/h or L/sL/s);
Design maximum ambient dry-bulb temperature (∘C∘C) and site altitude;
Maximum allowable fluid-side pressure drop (kPakPa or barbar);
Power supply voltage/frequency and fan preferences (EC or AC VFD).
