Heat pumps for Indian dairy plants: the 85 to 90°C pasteuriser loop, heated from refrigeration

We build Tetra Heat Pump systems for the 85 to 90°C hot water loop that drives HTST pasteurisation in an Indian dairy. They can take the heat for that loop from the refrigeration plant, which the same dairy rejects through a cooling tower today. In a fluid milk plant, centrifugation, homogenisation and pasteurisation use about 38% of the energy, and refrigeration about 19%. So the two largest loads in the building are a heat sink and a heat source, running at the same time. Evaporation and spray drying sit above the range and stay on the existing boiler.

What temperature does a dairy need?

Most of a liquid milk plant runs below 100°C. The table separates the milk from the hot water that heats it, because the heat pump serves the second.

Process step	Temperature	Delivery form	Heat pump
Milk reception and chilling	4°C or less	Chilled water	A heat source
Regeneration pre-warm of incoming milk	55 to 60°C	Product to product, inside the pasteuriser	Handled by regeneration
HTST pasteurisation, the milk	72 to 75°C, 15 seconds	Heated by the loop	Served through the loop
Pasteuriser hot water loop	85 to 90°C	Hot water	Fits
LTLT batch pasteurisation	62.8 to 65.6°C, 30 minutes	Hot water jacket	Fits
CIP caustic	70 to 85°C	Hot water	Fits
Washing and cleaning	40 to 60°C	Hot water	Fits
Post-pasteurisation cooling	10°C or less	Chilled water	A heat source
Sterilisation and evaporation	100 to 120°C	Process heat	At or above the top of the range
Spray dryer inlet air	180 to 200°C	Hot air	Does not fit

The law sets the floor. The Food Safety and Standards Act requires milk to reach at least 63°C for 30 minutes, or at least 71.5°C for 15 seconds.

The setpoint above that floor is worth watching. According to a BEE study of Indian dairies, each degree above 72°C adds roughly 10% to hot water consumption. It also adds about 8% to the refrigeration load, so a setpoint that has drifted upward costs twice.

Why does the hot water loop set the size?

HTST holds milk at 72 to 75°C for 15 seconds. The heat pump never heats that milk. It heats the water loop that drives heat across the plates of the existing exchanger.

That loop runs hotter than the milk, at 85 to 90°C, because the exchanger needs a temperature difference to move heat. So the figure that sizes the machine is the loop supply temperature. You can read it off your own instruments.

Regeneration does most of the work before the loop does. Hot pasteurised milk leaving the holding tube pre-warms the cold incoming milk to 55 to 60°C. In practice regeneration recovers 75 to 85% of the heat. The loop supplies only what regeneration leaves, so better regeneration means a smaller heat pump.

Because the heat pump only makes hot water, nothing in the product path changes. The plate exchanger, holding tube and diverter valve stay as they are, and so does your HACCP plan.

Where does the heat come from?

A dairy runs its refrigeration and its pasteurisation at the same time. Today the refrigeration heat leaves through a cooling tower while a boiler makes the hot water. A heat pump joins the two. Its source is the refrigeration condenser circuit, and its sink is the hot water loop.

Loads that reject heat	Share of plant energy	Loads that need heat	Share of plant energy
Refrigeration	19%	Centrifugation, homogenisation and pasteurisation	38%
		CIP	9.5%
		Process water	6%

The shares are for an Indian fluid milk plant, from the BEE and Shakti Sustainable Energy Foundation study of the dairy sector.

Many dairies already recover a slice of this heat. A desuperheater on an ammonia refrigeration plant gives hot water at 55 to 70°C, about 50 litres an hour per TR of refrigeration. A heat pump extends the same idea to 85 to 90°C, and to the full condenser load.

The temperature at which the two systems couple decides the result. A 2026 peer-reviewed study of an Indian dairy found a COP of 2.29 in its base case. Raising the coupling temperature to 50°C lifted the COP to 3.08. Our water source units reach COP 4.5 to 5.2 at 60°C output, and performance falls as output rises toward the 120°C ceiling.

What load does a dairy present?

The load follows the milk throughput and the regeneration efficiency. A worked example shows how much regeneration matters.

Take a plant pasteurising 10,000 litres an hour, with raw milk arriving at 4°C and a setpoint of 72°C. The full rise is 68°C. At 80% regeneration, the milk leaves the regeneration section at about 58°C. The loop then has to supply the last 14°C or so.

Using the hot water formula from our sizing guide, that is about 160 kW. Without regeneration, the same plant would need about 790 kW. These figures treat milk as water, which slightly overstates the load.

CIP adds a second shape. Caustic at 70 to 85°C arrives as a short, high-rate draw at the end of each run. Size the machine on the base load, and let a buffer store carry the CIP peak. A smaller machine running steadily does better than a large one cycling at part load.

Which fuel are you replacing?

Indian dairies burn furnace oil, rice husk, firewood, wood pellets and briquettes, and reduced coal availability is pushing more of them to switch. The answer depends on which of these you burn.

Incumbent fuel	Breakeven COP, Maharashtra tariff	Verdict
Light diesel oil at ₹107.65 per litre	0.67	The widest margin
Furnace oil at ₹71.99 per kg	1.10	Wins comfortably
PNG at ₹68 per SCM, Gujarat industrial	1.17	Wins comfortably
Biomass briquette at about ₹8,500 per tonne	3.33	Roughly parity
Coal, delivered at ₹6,000 per tonne	4.35	The heat pump costs more to run

Breakeven COP is the efficiency at which a heat pump costs exactly what the fuel costs. It is computed at the Maharashtra HT-I energy charge of ₹8.44 per kVAh. Against diesel, furnace oil and PNG, the saving lands in a 40 to 70% band.

Rice husk and firewood are cheap heat, like briquette. Against them, the case rests on labour, ash handling, storage space and turndown. The savings calculator runs the arithmetic on your own tariff and fuel price.

Liquid milk plants fit, and powder plants only in part

A liquid milk, curd or lassi plant is the clean fit. Almost all of its heat is the pasteuriser loop, CIP and washing water, all below 100°C.

A milk powder plant is different. Evaporation takes about 45% of its thermal energy and spray drying about 51%. Evaporation runs at 100 to 120°C and dryer inlet air at 180 to 200°C, so both stay on the boiler. On a powder plant the scope is the pasteuriser loop, CIP and washing water, which is a small share of the bill.

What evidence exists in India?

Published Indian evidence for dairy heat pumps is still thin, and three sources carry most of it.

• A 2026 peer-reviewed study in Energy Conversion and Management modelled a 344 kW single-stage heat pump replacing a wood-fired boiler at an Indian dairy. It found a COP of 2.29 and a simple payback of 4.93 years. At a 50°C coupling temperature, the COP rose to 3.08 and the payback fell to 3.07 years. It avoided about 388 tonnes of CO2e a year.
• The UNIDO, BEE and CII Gujarat dairy cluster compendium, September 2020, documents a 28 kW heat pump. It heated water from 22 to 80°C and displaced two 0.7 TPH diesel-fired boilers. Capital was ₹3.54 lakh against a net saving of ₹4.43 lakh a year, a 10-month payback.
• Our own dairy installation is a case study. It is 900 kW with heat recovery, and it serves the pasteuriser hot water loop.

What does FSSAI require of the heating system?

The Food Safety and Standards Act sets the pasteurisation minimums in the table above, and they apply to the milk. A heat pump that makes hot water never contacts product. The hygiene case rests on the plate heat exchanger the plant already runs.

Your site or a customer audit may require the equipment itself to be certified. We then obtain that certification for the project, to the standard you set.

A hot water loop at 85 to 90°C is below 100°C, so it is not a registered boiler under the Indian Boiler Regulations. The certified attendant on every shift and the annual inspection shutdown do not apply to that loop.

What to do next

Read three things off your own plant. They are the loop supply temperature, the refrigeration plant’s capacity in TR, and the CIP schedule with its peak draw.

Cooperative dairies buy through tenders, which take time. Private processors, with 73.3 million litres a day of registered capacity, usually decide faster. ADEETIE names food processing among its 14 eligible sectors, and the incentives guide explains what it funds.

The food and beverage page covers CIP and evaporator duties across the wider sector. Integration covers the tie-in to your controls, and maintenance covers what the machine needs once it runs. When you have the three numbers, send them to us.