Kettle cooking on pressurised hot water
How a ready-to-eat food plant cooking 6 tonnes of dal and gravies a day can heat its kettles with pressurised heat pump hot water instead of an LPG-fired boiler.
▶Video: Process hot water for food, dairy and beverages
V02 · 2–2.5 minPasteurisers, CIP, cooking and washing on stored hot water instead of boiler steam
Video coming soon01Problem statement
- Burn-on at the kettle wall. Steam jackets at 2–3 bar make the wall hot enough to scorch thick gravies and dal if stirring slows.
- Long simmer times. Dal and gravies simmer for an hour or more, so jackets draw heat for most of the shift.
- Small plant, full boiler. Running a boiler, its attendant and its water treatment for eight kettles is a large overhead.
- Losses between fuel and process. Burning LPG in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference plant makes ready-to-eat dal, curries and gravies for retail packs and food service. Eight 300-litre tilting jacketed kettles cook about 6 tonnes of product a day over two shifts. Kettles and utensils are washed with hot water.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Kettle batches, heating | 25 → 97 °C | 6,000 kg product/day, 15% jacket and lid losses | 511 |
| Simmering and evaporation | 95–98 °C | 8 kettles × 4 kW × 6 h | 192 |
| Kettle and utensil washing | 65 °C | 4,000 L/day, 30 → 65 °C | 163 |
| Storage and pipework standing losses | – | about 5% | 43 |
| Total useful heat | 908 | ||
Averaged over 16 running hours, the heat pumps need about 57 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- A SE-UHT air-source cascade, R245fa machine of about 60 kW, air-source cascade to 120 °C, sized per project.
- A 2,000 L insulated storage tank decouples the heat pumps from the process peaks.
- The LPG-fired steam boiler stays connected behind a normally closed valve as standby.
- Pressurised hot water at 115–120 °C circulates through the kettle jackets in place of steam.
- Each kettle has its own valve and temperature controller, so the cook can hold a gentle simmer.
- Wash water is heated from the same loop through a plate exchanger.
Selected equipment
| Machine | SE-UHT air-source cascade, R245fa |
|---|---|
| Capacity | about 60 kW, built to duty |
| Concept | air-source cascade to 120 °C, sized per project |
| COP used | 1.6 (estimate) |
| Supply temperature | 120 °C |
| Storage | 2,000 L insulated tank |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
TT-101 at the tank top starts the heat pumps below 112 °C and stops them at 120 °C. TIC-201 on each kettle controls jacket flow for heating and then a lower simmer setting. TT-102 at the tank bottom gives an early start before the morning batches. If the tank falls below 105 °C, the standby steam supply to the jackets is enabled.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per tonne of product | – | – |
| CO₂ per year | – | – |
06Benefits
Less scorching
Jacket water at 115–120 °C is gentler than steam, so product sticks less.
Easier simmer control
A flow valve gives smooth, low heat for simmering.
No IBR boiler for cooking
Kettles run without a steam boiler, attendant or condensate system.
Lower energy cost
Each kWh of electricity delivers about 1.6 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
No flame on site
No burner, flue or fuel tank for this duty, and no fuel deliveries to schedule.
Solar-ready
Running hours can be placed in daylight so rooftop solar supplies much of the electricity, which also cuts CO₂ further.
07Engineering pointers
Site data to collect
- Number and size of kettles
- Products, batch sizes and cook times
- Jacket type and pressure rating
- Washing water use
- Current LPG or steam use per day
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Jacket rating. Check kettle jackets are rated for the loop pressure, and that they have inlet and outlet connections suited to water flow.
- Heating time. Hot water heats more slowly than steam at first. Allow for this in batch planning or preheat ingredients.
- Pressurised loop. Hold the loop above about 2.5 bar(g) to keep water at 120 °C from flashing.
- Ambient correction. Ratings are at 20 °C air. Ask Sunniva for the correction at your site's winter design temperature.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
- Performance figure. The COP on this page is an engineering estimate, not a data sheet value. Sunniva engineering will confirm it for the actual source and supply temperatures.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.
Talk to us
Kettle cooking on pressurised hot water
How a ready-to-eat food plant cooking 6 tonnes of dal and gravies a day can heat its kettles with pressurised heat pump hot water instead of an LPG-fired boiler.
▶Video: Process hot water for food, dairy and beverages
V02 · 2–2.5 minPasteurisers, CIP, cooking and washing on stored hot water instead of boiler steam
Video coming soon01Problem statement
- Burn-on at the kettle wall. Steam jackets at 2–3 bar make the wall hot enough to scorch thick gravies and dal if stirring slows.
- Long simmer times. Dal and gravies simmer for an hour or more, so jackets draw heat for most of the shift.
- Small plant, full boiler. Running a boiler, its attendant and its water treatment for eight kettles is a large overhead.
- Losses between fuel and process. Burning LPG in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference plant makes ready-to-eat dal, curries and gravies for retail packs and food service. Eight 300-litre tilting jacketed kettles cook about 6 tonnes of product a day over two shifts. Kettles and utensils are washed with hot water.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Kettle batches, heating | 25 → 97 °C | 6,000 kg product/day, 15% jacket and lid losses | 511 |
| Simmering and evaporation | 95–98 °C | 8 kettles × 4 kW × 6 h | 192 |
| Kettle and utensil washing | 65 °C | 4,000 L/day, 30 → 65 °C | 163 |
| Storage and pipework standing losses | – | about 5% | 43 |
| Total useful heat | 908 | ||
Averaged over 16 running hours, the heat pumps need about 57 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- A SE-UHT air-source cascade, R245fa machine of about 60 kW, air-source cascade to 120 °C, sized per project.
- A 2,000 L insulated storage tank decouples the heat pumps from the process peaks.
- The LPG-fired steam boiler stays connected behind a normally closed valve as standby.
- Pressurised hot water at 115–120 °C circulates through the kettle jackets in place of steam.
- Each kettle has its own valve and temperature controller, so the cook can hold a gentle simmer.
- Wash water is heated from the same loop through a plate exchanger.
Selected equipment
| Machine | SE-UHT air-source cascade, R245fa |
|---|---|
| Capacity | about 60 kW, built to duty |
| Concept | air-source cascade to 120 °C, sized per project |
| COP used | 1.6 (estimate) |
| Supply temperature | 120 °C |
| Storage | 2,000 L insulated tank |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
TT-101 at the tank top starts the heat pumps below 112 °C and stops them at 120 °C. TIC-201 on each kettle controls jacket flow for heating and then a lower simmer setting. TT-102 at the tank bottom gives an early start before the morning batches. If the tank falls below 105 °C, the standby steam supply to the jackets is enabled.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per tonne of product | – | – |
| CO₂ per year | – | – |
06Benefits
Less scorching
Jacket water at 115–120 °C is gentler than steam, so product sticks less.
Easier simmer control
A flow valve gives smooth, low heat for simmering.
No IBR boiler for cooking
Kettles run without a steam boiler, attendant or condensate system.
Lower energy cost
Each kWh of electricity delivers about 1.6 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
No flame on site
No burner, flue or fuel tank for this duty, and no fuel deliveries to schedule.
Solar-ready
Running hours can be placed in daylight so rooftop solar supplies much of the electricity, which also cuts CO₂ further.
07Engineering pointers
Site data to collect
- Number and size of kettles
- Products, batch sizes and cook times
- Jacket type and pressure rating
- Washing water use
- Current LPG or steam use per day
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Jacket rating. Check kettle jackets are rated for the loop pressure, and that they have inlet and outlet connections suited to water flow.
- Heating time. Hot water heats more slowly than steam at first. Allow for this in batch planning or preheat ingredients.
- Pressurised loop. Hold the loop above about 2.5 bar(g) to keep water at 120 °C from flashing.
- Ambient correction. Ratings are at 20 °C air. Ask Sunniva for the correction at your site's winter design temperature.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
- Performance figure. The COP on this page is an engineering estimate, not a data sheet value. Sunniva engineering will confirm it for the actual source and supply temperatures.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.