The Challenge: Uneven Refrigerant Flow
In microchannel evaporators, cooling efficiency depends on how evenly refrigerant is distributed across dozens of parallel microchannels. When the refrigerant enters the inlet header in a two-phase state (liquid and vapor), the heavier liquid naturally settles at the bottom while the lighter vapor rises to the top.
This separation causes uneven feeding of the microchannels: some channels receive mostly vapor, others too much liquid. The result is reduced heat transfer efficiency, unstable operation, and significant performance losses.
In practical terms:
- Evaporators without any internal distributor can lose 25–35% of performance due to severe maldistribution.
- Systems equipped with conventional lateral-spraying distributors typically reduce losses, but still experience 10–15% performance degradation.
The Solution: Downward-Spraying Distributor (DSD)
To address this issue, Kaltra developed a new Downward-Spraying Distributor (DSD) architecture.
Instead of injecting refrigerant sideways inside the header — as in traditional designs — the DSD injects refrigerant vertically downward through precisely calibrated openings. This seemingly simple change produces a powerful effect:
- The downward spray works with gravity rather than against it.
- Liquid refrigerant is actively directed toward the lower region of the header.
- High-velocity jets create turbulence and fine mixing.
- Liquid and vapor phases are blended more evenly before entering the microchannels.
By mechanically disrupting natural phase separation, the DSD ensures that each microchannel receives a more consistent liquid–vapor mixture.
Near-Ideal Performance Achieved
Testing confirmed that evaporators equipped with Kaltra's DSD technology demonstrate performance losses as low as 1–3%, approaching ideal distribution conditions.
The system also maintains high distribution uniformity:
- At coil inclination angles up to 30°
- At inlet vapor qualities below 0.4
- Under realistic operating and installation conditions
Compared to conventional designs, the DSD concept represents a major improvement in evaporator stability, efficiency, and surface utilization.
Raising the Standard for Microchannel Technology
By solving one of the fundamental challenges of two-phase refrigerant flow inside horizontal headers, Kaltra's new distributor technology sets a new benchmark for microchannel heat exchanger performance.
The development reinforces Kaltra's commitment to advancing thermal management solutions through practical engineering innovation and measurable performance gains.
Photos: (Click photo to enlarge)
Source: Kaltra GmbH
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