What a Heat Pipe Does

A heat pipe is a sealed tube with a small amount of working fluid. Heat at one end evaporates the fluid; the vapour travels to the cold end, condenses, and releases the energy. A bundle of these tubes forms a passive exchanger with no motor and no mixing of airstreams.

Strengths

• No moving parts - essentially maintenance free
• Air streams never mix, so contamination risk is zero
• Works well in harsh or dirty environments

Weaknesses

• Lower effectiveness (typically 50 to 65 percent)
• Does not transfer moisture (sensible only)
• Less compact than a modern plate core at equal duty

Best Fit

Heat pipes suit locations where reliability matters more than peak efficiency: remote sites, industrial extracts, and systems where a failed motor would be expensive. For maximum energy savings in a normal building, a plate or rotary unit usually wins.

How the Air Moves

In a counterflow core the two airstreams run in opposite directions; in a crossflow core they cross at right angles. Counterflow lets the cold outgoing air meet the coldest part of the incoming stream, squeezing out more energy.

Effectiveness Difference

• Crossflow plate: typically 60 to 65 percent sensible
• Counterflow plate: typically 70 to 75 percent sensible

Trade-offs

Which to Specify

Crossflow fits most commercial ventilation where space and cost matter. Counterflow is the choice when every point of effectiveness counts, such as in passive-house or low-temperature heating systems.

Two Forms of Energy

Air carries energy as dry-bulb heat (sensible) and as water vapour (latent). Sensible recovery moves only the first; enthalpy recovery moves both.

Why It Matters

In a humid climate, a large part of the cooling load is the energy needed to remove moisture. A sensible-only exchanger leaves that moisture in the incoming air, so the cooling coil still works hard. An enthalpy exchanger pre-conditions both temperature and humidity.

Typical Results

• Sensible plate: ~70 percent temperature recovery, 0 percent moisture
• Enthalpy wheel: ~80 percent temperature, ~70 percent moisture
• Membrane plate: ~70 percent temperature, ~60 percent moisture

When Sensible Is Enough

In dry or cold climates, humidity control is not the bottleneck, so a simpler sensible plate core is the cost-effective choice.

When Enthalpy Pays Off

In tropical or subtropical buildings, enthalpy recovery often halves the dehumidification load and shortens the payback of the whole system.

When you specify an air-to-air heat recovery unit, the first fork in the road is fixed plate versus rotary (enthalpy) wheel. Both recover energy between supply and exhaust airstreams, but they behave very differently under real duty.

Side-by-side

When to choose a plate exchanger

Choose a plate core when airstreams are adjacent, you only need sensible recovery, contamination between streams must be zero, and budget is tight. Cold, dry climates are ideal because there is no moving part to freeze.

When to choose a rotary wheel

Choose a rotary wheel when you must control humidity (humid summers, museums, pools) or when the two airstreams are far apart and a plate will not fit. Accept the small purge-sector leakage as the price of latent recovery.

Decision summary

Pick plate for clean, sensible-only, contamination-free duties; pick rotary when latent recovery or distant airstreams dominate. See our plate and rotary selection guides for sizing.