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At CSTHEATEXCHANGER, we design and manufacture next-generation 5 mm and 7 mm Micro-Groove Copper Fin Tube Coils (Evaporators & Condensers) specifically engineered for small commercial refrigerators, reach-in display cases, refrigerated prep tables, beverage merchandisers, under-counter coolers, and medical refrigeration cabinets (standard heat exchange capacities engineered from 200 W to over 4,500 W per coil block). By replacing traditional bulky ∅9.52 mm (3/8") tubing with internally rifled ∅5.0 mm and ∅7.0 mm seamless deoxidized high-purity copper tubes, our coils achieve 35% to 50% higher internal heat transfer coefficients, reduce internal refrigerant volume by 50% to 65% (crucial for meeting the strict <150 g R290 charge limit under IEC 60335-2-89 / UL 60335-2-89), and cut copper raw material weight by up to 40%, delivering lighter, more compact, and highly energy-efficient refrigeration appliances.
The transition from conventional ∅9.52 mm (3/8") or ∅12.7 mm (1/2") tubes to smaller diameters (∅5 mm and ∅7 mm) is driven by fundamental heat transfer physics and refrigerant phase-change dynamics:
THERMODYNAMIC & AERODYNAMIC COMPARISON: 9.52mm VS. 5mm/7mm TUBES
[CONVENTIONAL 9.52mm (3/8") TUBE] [CST 5mm / 7mm MICRO-GROOVE TUBE]
┌────────────────────────────────────────┐ ┌────────────────────────────────────────┐
│ Thick Thermal Boundary Layer │ │ Thin Thermal Boundary Layer │
│ Large Internal Volume (High R290 Charge│ │ -60% Internal Volume (Low R290 Charge) │
│ Large Air-Side Form Drag & Wake Eddies │ │ Streamlined Profile, Low Air Friction │
│ Heavy Copper Weight & Commodity Cost │ │ -40% Copper Weight, Higher Burst Limit │
└────────────────────────────────────────┘ └────────────────────────────────────────┘================================================================================
PHYSICAL & THERMAL PROPERTY COMPARISON ACROSS TUBE DIAMETERS
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Engineering Parameter Traditional 9.52mm (3/8") CST 7.0mm Micro-Groove CST 5.0mm Micro-Groove
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Tube Outer Diameter (OD) 9.52 mm (0.375") 7.00 mm (0.275") 5.00 mm (0.197")
Internal Cross-Sectional Area ~50.2 mm² (Baseline 100%) ~26.4 mm² (-47% Volume) ~12.5 mm² (-75% Volume)
Internal Heat Transfer Coeff. Baseline (1.0x) Enhanced (+30% to +40%) Ultra-High (+50% to +70%)
Internal Rifling Enhancement Smooth or Basic Grooving High-Density Micro-Fins (55-65) Micro-Rifled Grooves (40-50)
Air-Side Form Drag Profile Large Wake Turbulence Medium Streamlined Profile Minimal Wake Resistance
Refrigerant Charge Volume High Charge Requirement Low Charge (~50% Reduction) Ultra-Low (~65% Reduction)
Inherent Burst Pressure Rating 80 - 100 bar 120 - 140 bar 150 - 180+ bar
Copper Material Weight Savings Baseline (0% Savings) 25% - 30% Weight Reduction 35% - 42% Weight Reduction
================================================================================CSTHEATEXCHANGER 5 mm5 mm and 7 mm7 mm tubes feature precision internal helical micro-grooves. These micro-fins increase internal wetted surface area by 1.8× to 2.2×1.8× to 2.2×, induce intense spiral turbulence that thins the refrigerant thermal boundary layer, and promote annular liquid film evaporation/condensation.
Smaller tube profiles reduce the projected frontal obstruction area, minimizing wake eddies behind each tube row. This lowers air-side pressure drop across the coil by 15% to 25%15% to 25%, allowing equipment designers to use lower-wattage, quieter fans.
Global environmental regulations (EU F-Gas Directive, US EPA SNAP, Kigali Amendment) mandate low-GWP refrigerants in commercial refrigeration. Safety standards strictly limit hydrocarbon charges to maximum 150 g150 g (or 500 g500 g with approved safety protocols):
R290 PROPANE CHARGE COMPLIANCE IN COMMERCIAL REACH-IN COOLERS
======================= [STANDALONE COMMERCIAL COOLER] =======================
• Target Charge Limit: < 150g R290 (Flammability Class A3 Safety Compliance)
│
▼
┌────────────────────────────────────────────────────────────────────────────┐
│ CHALLENGE: 9.52mm Coils Require 220g - 280g R290 -> FAILS SAFETY LIMIT │
├────────────────────────────────────────────────────────────────────────────┤
│ SOLUTION: CSTHEATEXCHANGER 5mm / 7mm Coils Require 90g - 130g R290 │
│ -> FULLY COMPLIANT WITH IEC / UL 60335-2-89 SAFETY STANDARDS │
└────────────────────────────────────────────────────────────────────────────┘By reducing internal refrigerant volume by up to 65%65%, CSTHEATEXCHANGER 5 mm5 mm and 7 mm7 mm evaporators and condensers allow multi-door commercial refrigerators and display cases to deliver high refrigeration capacities while remaining safely below the 150 g150 g flammability limit.
CSTHEATEXCHANGER® ADVANCED FIN-TO-TUBE EXPANSION INTERFACE
┌────────────────────────────────────────────────────────────────────────┐
│ HIGH-EFFICIENCY CORRUGATED LOUVERED ALUMINUM FINS (Hydrophilic Coated) │
├────────────────────────────────────────────────────────────────────────┤
│ MECHANICAL MECHANICAL BALL EXPANSION INTERFACE (100% Zero-Gap Contact) │
├────────────────────────────────────────────────────────────────────────┤
│ INNER-GROOVED DHP COPPER TUBES (Ø 5.0 mm or Ø 7.0 mm | C12200 Copper) │
├────────────────────────────────────────────────────────────────────────┤
│ ROBUST COPPER RETURN BENDS (High-Purity Automated Lead-Free Brazing) │
└────────────────────────────────────────────────────────────────────────┘Achieving perfect metal-to-metal contact between small ∅5 mm∅5 mm tubes and aluminum fin collars requires precision expansion tooling. CSTHEATEXCHANGER uses automated hydraulic expansion systems with precision carbide balls, ensuring 100%100% uniform fin collar contact without wall thinning or internal groove flattening.
Louvered & Sine-Wave Corrugated Fins: Maximizes air turbulence and heat transfer in compact reach-in evaporator/condenser footprints.
Hydrophilic Blue Fin / Gold Fin Coating: Accelerates condensate drainage on evaporators without moisture carryover.
Electrophoretic E-Coat: Full immersion coating providing over 1,500 hours of salt spray protection1,500 hours of salt spray protection for coastal and harsh kitchen environments.
(Note: The following engineering parameters represent standard manufacturing design envelopes. Exact coil dimensions, row depths, fin pitches, and circuit paths are custom-engineered to customer appliance specifications.)
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CSTHEATEXCHANGER 5mm & 7mm SMALL REFRIGERATOR COIL (CST-SFC SERIES)
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Engineering Parameter Standard Manufacturing & Design Range
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Heat Exchange Capacity Range Typical: 200 W to 4,500+ W per coil module (Customizable)
Primary Tube Diameters Ø 5.0 mm (0.197") and Ø 7.0 mm (0.275") Outer Diameter
Tube Internal Profile Micro-Grooved Inner-Rifled Helical Ridges or Smooth Bore
Tube Metallurgy Seamless High-Purity Phosphorus-Deoxidized Copper (C12200 / Cu-DHP)
Fin Materials & Profiles High-Purity Aluminum (Al 1100 / 8011), Hydrophilic Blue Fin, Epoxy, SS
Fin Surface Enhancements Corrugated Sine-Wave, Enhanced Louvered, or Flat Anti-Fouling
Fin Spacing / Pitch Range 1.8 mm to 6.0 mm (4 to 14 FPI) for Evaporators and Condensers
Coil Circuiting Architectures Multi-Circuit Balanced Counter-Flow, Single-Pass, Cross-Flow
Refrigerant Compatibility R290 (Propane), R600a (Isobutane), R134a, R404A, R452A, R513A, R448A
Operating Design Pressure Up to 45 bar (653 psi); Proof Burst Pressure > 140 bar (2,030 psi)
Leakage Verification Standard 100% Helium Mass Spectrometer Vacuum Leak Testing (< 1x10⁻⁶ mbar·l/s)
Quality & Environmental Codes UL 207, CE / PED, ISO 9001, RoHS, REACH, IEC 60335-2-89 Compliant
================================================================================Compared to traditional ∅9.52 mm (3/8") coils, 5 mm and 7 mm coils reduce internal refrigerant volume by 50%–65%, enabling compliance with <150 g R290 Propane flammability safety limits. They also increase heat transfer efficiency by 30%–50%, reduce copper material weight by 35%–40%, and lower air-side fan power consumption.
If a coil simply substitutes smaller tubes into an unchanged circuit layout, pressure drop would increase. However, CSTHEATEXCHANGER custom-engineers optimized multi-circuit, multi-pass distribution configurations that balance refrigerant mass flow velocity, maintaining low pressure drop while maximizing convective boiling and condensing coefficients.
Yes. We support global refrigeration equipment manufacturers with rapid prototyping services, providing engineered 3D CAD models, thermodynamic selection datasheets, and physical prototype coils for calorimeter performance and DOE / Energy Star compliance testing.
Achieve R290R290 compliance, cut copper raw material costs, and boost refrigeration efficiency with CSTHEATEXCHANGER:
Custom 5 mm5 mm & 7 mm7 mm Micro-Groove Copper Evaporators & Condensers
Engineered for Low-Charge Eco-Refrigerants (R290 / R600a with <150 g Limit)
35% to 50% Higher Heat Transfer Coefficient than Conventional ∅9.52 mm Tubes
Up to 40% Copper Weight Reduction for Significant Material Cost Savings
Hydrophilic Blue Fin, Gold Fin, and Full Immersion Electrophoretic E-Coat Options
100% Helium Mass Spectrometer Leak Tested with UL / CE / RoHS Certification
Contact our specialized small-diameter thermal engineering team today with your refrigeration cabinet capacity, target evaporating/condensing temperatures, dimensional footprint, and refrigerant choice for custom thermal selections, 3D CAD drawings, and competitive factory-direct pricing.
Website: https://www.cstheatexchanger.com/
Technical Inquiries: info@cstheatexchanger.com
