BROAD India
Direct Fired vs. Indirect Fired Absorption Chillers: Which Fits Your Infrastructure?
Jan 27, 2026
8 min read
Energy & Industrial Efficiency
Direct Fired vs. Indirect Fired Absorption Chillers: Which Fits Your Infrastructure?
Choosing an absorption cooling solution depends on your facility's energy sources, infrastructure, and operational priorities. Both direct-fired and indirect-fired VAM chillers produce chilled water using thermal energy rather than electricity, but their energy paths differ significantly.
Understanding the Core Difference 🔍
| Chiller Type | How It Works | Energy Flow |
|---|---|---|
| Direct-Fired VAM | Burner integrated in chiller. Natural gas, diesel, or fuel oil combusted inside the unit. | Fuel → Direct combustion → Heat → Absorption cycle → Chilled water |
| Indirect-Fired VAM | Receives heat from external source: steam, hot water, or exhaust gases. | Fuel → External equipment → Steam/Hot water/Exhaust → Absorption cycle → Chilled water |
Infrastructure Requirements Comparison 🏗️
| Requirement | Direct-Fired | Indirect-Fired |
|---|---|---|
| External Heat Source | Not required | Required (boiler, generator, process heat) |
| Fuel Supply | Gas line or diesel tank | Depends on heat source |
| Steam Piping | None | Required for steam systems |
| Exhaust Ducting | Simple flue stack | Complex for exhaust recovery |
| Combustion Air | Required | Not required |
| Space Requirements | Compact, single unit | Distributed (heat source + chiller) |
| Environmental Permits | Combustion permits required | May not need if using existing source |
When Direct-Fired Makes Perfect Sense 🔥
- New facilities without steam infrastructure: Avoid boiler cost (₹80 lakhs–1.2 cr).
- Commercial buildings (hotels, hospitals, offices).
- Grid-constrained areas with gas access.
- District cooling plants with large central capacity.
When Indirect-Fired Excels ♻️
- Facilities with existing steam infrastructure.
- Waste heat recovery applications.
- Combined Cooling, Heating & Power (CCHP).
- Industrial plants with multiple heat sources.
Efficiency & Performance ⚡
| Chiller Type | COP | Fuel & Flexibility |
|---|---|---|
| Direct-Fired | 1.20–1.35 | Natural gas, LPG, diesel, dual-fuel |
| Indirect-Fired | 0.70–1.35 | Steam, hot water, exhaust heat |
Capital Cost (500 TR System) 💰
| Chiller Type | Equipment | Aux & Installation | Total CAPEX |
|---|---|---|---|
| Direct-Fired VAM | ₹6.5–7.5 cr + gas train ₹0.4–0.6 cr | ₹1.5–2 cr | ₹8.5–10.1 cr |
| Indirect-Fired Steam VAM | ₹3.2–3.8 cr + steam integration ₹0.4–0.8 cr | ₹1.8–2.2 cr | ₹5.4–6.8 cr |
Operating Cost Reality 🏭
- Direct-Fired: Fuel dominates cost; best where fuel cheaper than electricity.
- Indirect-Fired Waste Heat: Lowest operating cost.
- Indirect-Fired Steam: Higher cost unless high-pressure steam is free/available.
Decision Framework ✅
- Choose Direct-Fired: No steam/waste heat, gas available, commercial buildings.
- Choose Indirect-Fired: Steam/waste heat available, CCHP, industrial plants.
- Hybrid: Indirect base load + direct-fired peak load.
💡 Need Help Choosing the Right Absorption Chiller?
BROAD India's engineers can guide you based on your heat sources and infrastructure.
BROAD Air Conditioning India Pvt. Ltd. (BROAD India) is a subsidiary of BROAD Group.
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