污水源热回收：再利用排水能量

The hidden reservoir

Showers, wash-down, and process drains leave buildings at 25-40C – warm enough to be a valuable heat source. Wastewater (drain-water) heat recovery captures it before it disappears down the sewer.

工作原理

• 排水（废水）换热器 将盘管缠绕或置于中水水流中，对进入的冷水进行预热。
• 热泵 将低品位废水温度提升至可用于生活热水或空间供暖的水平。
• Unlike air-to-air recovery, this is a water-to-water loop – see 空气-空气 与 空气-水 对比.

Best-fit buildings

泳池、健身房、学生宿舍，以及有连续温排水的洗衣房。与以下配对： 休闲设施回热指南 用于泳池。

Design cautions

• 结垢与异味：使用易检修、可清洁的换热器以及毛发／截留过滤器。
• 流量匹配：回热随排水量变化，因此应按同时峰值使用量选型。

投资回收

在热水需求高的场所，排水回热通常2–3年即可回收投资，并削减热水加热能耗30–50%。通过以下进行验证： 投资回收期计算.

Temperature lift and the heat pump

Drain water at 25 to 40C is too cool for direct use but ideal as a heat-pump source. A heat pump lifts that low-grade warmth to the 45 to 60C range needed for domestic hot water or space heating, often at a coefficient of performance well above unity. Pairing a drain-water coil with a heat pump captures more of the available energy than passive recovery alone, which matters where hot-water demand is constant.

Flow matching and storage

Recovery tracks drain volume, so the exchanger and any buffer tank should be sized to peak simultaneous use rather than the daily average. A small thermal store smooths the mismatch between when warm water leaves and when it is needed, letting the heat pump run at steadier, more efficient conditions instead of hunting with the drain flow.

Hygiene and access

Greywater carries hair, grease, and odor potential, so the exchanger must be accessible for cleaning and protected by a strainer or hair trap upstream. Choose a design that can be flushed or descaled without removing major piping, and confirm materials resist the mildly corrosive drain environment. Trend the recovered energy to confirm the coil stays clean.

常见问题

What temperature is drain water and can it be used?
Drain water leaves at 25 to 40C. It is too cool for direct use but ideal as a heat-pump source for domestic hot water or space heating.

Which buildings benefit most from drain-water recovery?
Swimming pools, gyms, student residences, and laundries with a continuous warm drain flow benefit most.

What design cautions apply?
Fouling and odor: use accessible, cleanable exchangers and a hair or trap filter upstream. Size to peak simultaneous flow, not the daily average.

What payback is typical?
In high hot-water-demand sites, drain-water recovery often pays back in 2 to 3 years and cuts water-heating energy by 30 to 50 percent. Validate with a payback calculation.

常见问题

What temperature is drain water and can it be used?

Drain water leaves at 25 to 40C. It is too cool for direct use but ideal as a heat-pump source for domestic hot water or space heating.

Which buildings benefit most from drain-water recovery?

Swimming pools, gyms, student residences, and laundries with a continuous warm drain flow benefit most.

What design cautions apply?

Fouling and odor: use accessible, cleanable exchangers and a hair or trap filter upstream. Size to peak simultaneous flow, not the daily average.

What payback is typical?

In high hot-water-demand sites, drain-water recovery often pays back in 2 to 3 years and cuts water-heating energy by 30 to 50 percent. Validate with a payback calculation.