How Water-Cooled Bare Tube Condensers Work?

How Water-Cooled Bare Tube Condensers Work (Most Common for Commercial/Industrial Ice Machines)

Water is a far more efficient heat transfer medium than air (its thermal conductivity is ~23x higher), making water-cooled bare tube condensers ideal for high-capacity ice machines (e.g., 1–50 ton/day output, used in restaurants, fisheries, or beverage plants). Their operation follows 4 key steps:

Step 1: Refrigerant Enters the Condenser (Superheated Vapor)

The high-temperature, high-pressure refrigerant vapor (from the compressor) flows into the condenser’s refrigerant inlet header—a manifold that distributes the vapor evenly into a bundle of smooth, bare copper (or cupronickel) tubes. These tubes are arranged in rows (staggered or inline) to maximize contact with the cooling water.

Step 2: Cooling Water Circulates Around the Tubes (Countercurrent Flow)

Cooling water (sourced from a municipal supply, cooling tower, or well) is pumped into the condenser’s shell (the outer chamber surrounding the tube bundle). Crucially, the water flows in a countercurrent direction to the refrigerant:

Water enters near the condenser’s refrigerant liquid outlet (where the refrigerant is already cool).

Water exits near the refrigerant vapor inlet (where the refrigerant is hottest).

This countercurrent design maximizes the temperature difference (ΔT) between the refrigerant (inside the tubes) and the water (outside the tubes) at every point in the condenser. A larger ΔT means faster, more efficient heat transfer—critical for condensing the refrigerant quickly.

Step 3: Heat Transfer Occurs Through the Bare Tubes

Heat from the superheated refrigerant (inside the tubes) is transferred in two stages:

Desuperheating: First, the refrigerant releases “sensible heat” (heat that changes temperature but not state) to the water, cooling from 50–70°C down to its saturation temperature (the temperature at which it starts to condense, e.g., 35–45°C for R404A).

Condensation: Next, the refrigerant releases “latent heat” (heat that changes state but not temperature) as it turns from vapor into liquid. This is the most heat-intensive stage—latent heat accounts for ~80% of the total heat the condenser removes.

The bare tube’s smooth copper surface is key here: copper has excellent thermal conductivity (~401 W/m·K), so heat flows quickly through the tube walls to the circulating water. Unlike finned tubes, the smooth surface has no crevices for scale (mineral deposits from water) to accumulate, ensuring consistent heat transfer over time.

Step 4: Liquid Refrigerant Exits; Heated Water is Disposed

The condensed liquid refrigerant collects in the condenser’s outlet header, then flows to the expansion valve to start the next phase of the cycle.

The water, now heated by absorbing the refrigerant’s heat (typically 3–10°C warmer than its inlet temperature), exits the condenser. It may be:

Discharged to a drain (for small machines), or

Recycled to a cooling tower (for large machines, to save water).