FAQ — Help Center
Heat Exchanger FAQ — Technical, Commercial & Quality Questions Answered
General · OEM Custom · Quality & Certifications · Technical · Commercial
Answers to the most common questions from HVAC engineers, refrigeration system designers, procurement managers, and service technicians. Can’t find your answer? Contact our engi…
General — What We Make and How It Works
A heat exchanger is a device designed to transfer thermal energy between two or more fluids at different temperatures without mixing them. In refrigeration and HVAC applications, the refrigerant absorbs heat in the evaporator (cooling the space or airflow) and rejects heat in the condenser (releasing it to the ambient environment). Domi manufactures both condensers and evaporators for OEM, commercial, and industrial applications.
A condenser is the heat exchanger where the refrigerant rejects heat and changes from gas to liquid. In a refrigerator, the condenser is usually on the back or bottom of the unit, releasing heat to the room. An evaporator is where the refrigerant absorbs heat and changes from liquid to gas. In a refrigerator, it is inside the cabinet, absorbing heat from the stored food.
Domi manufactures wire tube condensers, roll bond evaporators, fin-and-tube coils (copper or aluminum), microchannel condensers, plate heat exchangers, shell-and-tube heat exchangers, brazed plate heat exchangers, and custom automotive thermal components. We cover residential, commercial, HVAC, industrial refrigeration, and automotive thermal management applications.
Our heat exchangers are designed and tested for R134a, R600a (isobutane), R290 (propane), R32, R410A, R407C, R744 (CO2), R1234yf, ammonia (R717), and glycol circuits. We confirm refrigerant compatibility on a per-design basis and can modify tube materials, wall thickness, and joining methods to meet the pressure and chemical compatibility requirements of each refrigerant.
Both. We maintain stock of standard wire tube condensers, fin coils, and replacement coils for common commercial refrigeration applications. We also design and manufacture fully custom heat exchangers from customer specifications — from prototype to mass production. Custom projects start with a DFM review and typically deliver first samples within 7–14 days.
OEM & Custom Manufacturing
For standard products, MOQ is typically 50–200 units depending on product type. For custom designs, we offer first-sample orders from 5 units with no tooling surcharge for most products. Mass production MOQ is agreed per project. We do not require large upfront commitments for new product development.
Standard prototype delivery is 7 working days from approved drawing. Complex designs with new tooling requirements may require 10–14 days. Our rapid prototyping track is available for urgent new product development and delivers first samples in 5 days at a small premium.
Yes. Send us the original unit (or detailed dimensional measurements and photos), and we will reverse-engineer a functional equivalent. We typically improve on the original in at least one dimension — thermal performance, weight, or cost — during the reverse engineering process.
Yes. Our engineering team provides free application review, DFM (Design for Manufacturability) assessment, CFD thermal simulation, and material selection guidance as part of the quotation process for custom projects. We operate as a thermal engineering partner, not just a contract manufacturer.
Yes. We specialize in reduced-charge circuit designs for R290 (propane), R600a (isobutane), and R32. Our engineers apply circuit optimization to minimize refrigerant inventory while maintaining full thermal performance, helping customers comply with EN 60335-2-24 and IEC 60335-2-89 charge limits.
Quality, Testing & Certifications
Domi is certified to ISO 9001:2015 (quality management), IATF 16949:2016 (automotive quality), and CE marking for applicable products. Our products comply with ROHS and REACH directives. ASME certification is available for pressure vessel components upon request. Certificate copies are available on request.
Yes. Every heat exchanger that leaves our facility undergoes 100% helium mass spectrometer leak testing. Leak threshold is set at <1x10-6 Pa·m3/s — more sensitive than hydrostatic pressure testing. Dimensional inspection is performed on 100% of components for critical dimensions, with full measurement reports available.
Our in-house salt spray test chamber (per ASTM B117 / ISO 9227) validates anti-corrosion coating performance. Standard commercial refrigeration coatings are tested to 500 hours minimum. Our premium epoxy coating system achieves 10,000 hours without red rust formation — verified with independent third-party testing.
Yes. Under our IATF 16949 quality system, we support PPAP Level 1 through Level 5 submissions. Full PPAP packages include PFMEA, Control Plan, MSA (Gauge R&R), SPC data (minimum 30-piece initial study), Material Certifications, and Appearance Approval. IMDS data submission is available.
Each shipment includes a Certificate of Conformance (COC), dimensional inspection report, leak test records, and material compliance declaration (ROHS/REACH). Batch records are retained for a minimum of 10 years. For automotive orders, full production traceability to raw material heat number is maintained.
Technical Questions
Heat exchanger capacity (Q) is calculated as Q = U x A x LMTD, where U is the overall heat transfer coefficient, A is the heat transfer area, and LMTD is the Log Mean Temperature Difference between the two fluids. For refrigeration applications, capacity must match the system’s heat load at design operating conditions. Our engineering team can perform this sizing calculation for you — submit your operating conditions (temperatures, flow rates, fluids) via the RFQ form.
Fin pitch (fins per inch, FPI) affects both heat transfer performance and airside pressure drop. Higher FPI (denser fins) increases surface area but also increases resistance to airflow. For clean air applications (residential HVAC), 12–16 FPI is typical. For dirty or high-humidity environments (commercial refrigeration), 4–8 FPI is preferred to reduce fouling. For freezer applications, 1–4 FPI may be required to manage frost accumulation.
Copper offers higher thermal conductivity and better joining reliability but costs more. Aluminum is lighter and increasingly preferred for automotive and HVAC applications where weight matters. Stainless steel is used for high-temperature or corrosive applications. Our material selection guide (available for free download) covers all trade-off factors including cost, conductivity, corrosion resistance, and refrigerant compatibility.
Microchannel heat exchangers use flat multi-port aluminum tubes with very small internal hydraulic diameters (typically 0.8–2.0mm). Advantages include: lower refrigerant charge, lower airside pressure drop, higher thermal efficiency per unit volume, and lighter weight. They are ideal for automotive AC, commercial RTU condensers, and high-efficiency residential HVAC. Limitations include higher sensitivity to fouling and restrictions in high-humidity evaporator applications.
Corrosion protection depends on the corrosion mechanism. For coastal saltair (chloride) environments, epoxy coating, phenolic coating, or e-coat provides the best protection. For industrial environments with acidic gases (SO2, H2S), phenolic coating or stainless steel fin material is recommended. For food processing environments with ammonia exposure, specify aluminum or stainless steel — avoid copper. Our anti-corrosion coating comparison guide details performance data for each coating type.
Commercial & Logistics
Standard products (wire tube condensers, replacement coils): 5–10 working days from order confirmation. Custom designs (first sample): 7–14 working days from drawing approval. Custom production orders: 3–5 weeks from purchase order. Expedited production is available for qualified customers — contact us to discuss urgent requirements.
We ship worldwide. Standard shipping destinations include: USA, Canada, Germany, Italy, France, UK, Netherlands, Poland, Australia, Japan, South Korea, India, Brazil, and Mexico. For countries with import restrictions or high customs complexity, our export team can advise on documentation requirements and recommend freight forwarding partners.
Yes. We offer private label manufacturing for distributors and resellers who wish to source heat exchangers under their own brand. We do not proactively advertise our OEM customers and sign NDAs as standard practice. Our production processes, quality records, and tooling are maintained separately per customer.
Standard terms for new customers: 50% deposit, 50% before shipment (TT). For established customers with credit history: 30% deposit, 70% Net 30 from Bill of Lading date. We accept T/T bank transfer, L/C (for orders over $50,000 USD), and PayPal for sample orders. All pricing is in USD.
Submit your RFQ through our contact form with: product type, dimensional drawings or specifications, operating conditions (temperatures, refrigerant, capacity), required quantity, and target delivery date. We will respond with a technical review and commercial quotation within 24–48 business hours. For standard products, provide model dimensions and we will match or cross-reference from our catalog.
Still Have a Question?
Our application engineers respond within 24 business hours. Ask us anything about heat exchanger selection, custom design, or order logistics.