Stainless Steel Coil Tube for Heat Pump Dual-Supply Unit Heat Exchangers

Product Overview

The Stainless Steel Coil Tube (盘管, Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component designed for integration into heat exchangers within heat pump dual-supply units (热泵两联供机组). These units provide simultaneous heating and cooling functions for residential and commercial buildings. The coil tube serves as the primary heat transfer medium, circulating refrigerant or water through its serpentine geometry to maximize thermal exchange efficiency.

Based on extensive research into preventing icing accumulation at the bottom of coil heat exchangers, this product incorporates advanced design features that address the critical challenge of frost formation in low-temperature operating environments. The coil tube is engineered to maintain consistent heat transfer performance even under conditions prone to condensation and ice buildup, thereby extending equipment service life and ensuring reliable operation throughout seasonal cycles.

Material & Properties

The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical durability under extreme thermal cycling conditions.

Specifications

Parameter Specification Standard / Tolerance
Outer Diameter (OD) φ7.0 mm / φ9.52 mm / φ12.0 mm ±0.1 mm
Wall Thickness 0.5 mm – 1.0 mm ±0.05 mm
Inner Diameter (ID) φ6.0 mm / φ8.5 mm / φ11.0 mm ±0.05 mm
Coil Diameter φ150 mm – φ400 mm ±2 mm
Coil Length Custom (up to 300 m per coil) ±50 mm
Tube Pitch (间距) 14 mm – 25 mm ±0.5 mm
Row Spacing 14 mm – 25 mm ±0.5 mm
Max. Working Pressure 2.5 MPa ASME B31.5
Hydrostatic Test Pressure 3.75 MPa (1.5× working pressure) GB/T 14976
Heat Transfer Coefficient ≥ 60 W/(m²·K) ASTM A213
Surface Treatment Pickled & Passivated (酸洗钝化) GB/T 19228
End Form Flat-cut / Beveled / Flanged Per customer drawing
Applicable Refrigerants R410A, R32, R134a, R407C, Water/Glycol ASHRAE 34

Manufacturing Process

The coil tube is produced through a multi-stage precision manufacturing process that ensures dimensional accuracy, surface integrity, and reliable performance in demanding heat exchanger applications.

  1. Material Selection & Inspection: Cold-rolled stainless steel strip or seamless tubing conforming to ASTM A269 / GB/T 14976 is received and subjected to spectroscopic analysis (OES) and mechanical testing to verify chemical composition and physical properties.
  2. Coil Forming (盘管成型): The straight tube is fed through a precision coiling machine equipped with CNC-controlled bending heads. The forming process employs progressive bending with controlled reduction rates (≤ 3% per pass) to prevent wall thinning, ovality, or micro-cracking. The coil geometry is optimized to promote uniform airflow distribution and facilitate condensate drainage from the bottom section.
  3. Anti-Icing Structural Design: Drawing upon research findings regarding heat pump dual-supply unit performance, the coil tube geometry incorporates asymmetric pitch patterns and optimized drain angles (≥ 5°) to prevent condensate pooling and subsequent ice formation at the bottom of the heat exchanger. This design ensures continuous heat transfer even in sub-zero ambient conditions.
  4. Welding & Brazing: Tube-to-fin joints and tube-to-header connections are fabricated using TIG (Tungsten Inert Gas) welding or high-temperature silver brazing under argon shielding. Joint integrity is verified through dye penetrant testing (PT) and helium leak testing at 10⁻⁹ mbar·L/s sensitivity.
  5. Surface Treatment: Post-forming pickling and passivation (酸洗钝化处理) removes oxide scale and contamination, establishing a protective chromium oxide layer that enhances long-term corrosion resistance in humid, chlorinated environments.
  6. Quality Assurance & Testing: Each coil assembly undergoes dimensional inspection (OD, wall thickness, coil diameter, pitch), hydrostatic pressure testing, and thermal performance verification. Random samples are subjected to accelerated corrosion testing (salt spray per ASTM B117, ≥ 500 hours) and low-temperature impact testing (Charpy V-notch at −40°C).

Applications

The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. is specifically engineered for the following applications:

Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and compliances:

Unique Selling Points

Anti-Icing Innovation: The coil tube geometry is specifically designed based on published research into heat pump dual-supply unit icing prevention. Asymmetric coil pitch and optimized bottom-section drainage angles eliminate condensate accumulation, reducing ice formation by up to 70% compared to conventional uniform-pitch coils.