Inputs
Use the ratio mode to hit a target by mixing hot and cold water, or use fixed volumes to compute the resulting temperature. Add heater/chiller power for time estimates.
Example Data
This example shows a practical mixing plan plus heating energy for a small batch.
| Total Volume | Start Temp | Target Temp | Hot Temp | Cold Temp | Hot Volume | Cold Volume | Energy Needed |
|---|---|---|---|---|---|---|---|
| 20 L | 18 °C | 20 °C | 55 °C | 10 °C | 4.44 L | 15.56 L | 167.4 kJ |
Formula Used
Mixing to reach a target temperature:
When mixing hot and cold water into a total volume V:
V_hot = V × (T_target − T_cold) ÷ (T_hot − T_cold),
and V_cold = V − V_hot.
Energy to change temperature:
Q = m × c_p × (T_target − T_start),
where m ≈ V (kg) for water and c_p ≈ 4186 J/(kg·°C).
Time estimate with optional heat exchange:
With heater/chiller power P and heat exchange coefficient UA:
m c_p dT/dt = P − UA(T − T_ambient).
If UA = 0, then t ≈ m c_p |ΔT| ÷ |P|.
How to Use This Calculator
- Enter total volume and your current (start) solution temperature.
- Set the target temperature you want before feeding or watering.
- Choose mixing mode: ratio for a target, or fixed to test a blend.
- Provide hot/cold water temperatures based on your sources.
- Optional: enter heater or chiller power and efficiency for timing.
- Optional: add UA and ambient temperature to account for heat loss.
- Calculate, then download a CSV or PDF report for your logs.
Article
Why solution temperature matters in gardening
Nutrient uptake is closely tied to root-zone temperature because water viscosity, dissolved oxygen, and membrane transport all change with heat. Cool solutions can slow growth, while overly warm solutions reduce oxygen availability and can stress roots. A simple temperature plan helps keep irrigation consistent across seasons, especially in container gardens and recirculating systems.
Using mixing to reach a target temperature
When you have two water sources, mixing is often the fastest correction method. The calculator estimates hot and cold volumes required to reach a target, based on conservation of energy for water. This is useful when you need a ready-to-use batch without waiting for equipment to raise or lower temperature.
Estimating heating or cooling energy and time
The energy estimate uses the water heat capacity to convert temperature change into kJ and kWh. If you enter heater or chiller power, the tool provides a practical time estimate and can optionally include heat exchange to ambient air using a UA value. This supports realistic planning for mixing tanks and reservoirs.
Example data for a typical small batch
Example inputs: total volume 20 L, start 18 °C, target 20 °C, hot 55 °C, cold 10 °C, heater 300 W at 90% efficiency, UA 0 W/°C. Example outputs: hot volume 4.44 L, cold volume 15.56 L, energy 167.4 kJ (0.046 kWh), estimated heating time about 10.3 minutes without losses.
Operational tips for consistent results
Measure actual water temperatures before mixing, and re-check the final blend with a thermometer. Adjust targets gradually during cold snaps or heat waves to avoid root shock. If you log results, the CSV/PDF reports can help standardize practices across workers and seasons, improving repeatability for sensitive crops.
FAQs
1) What temperature range is generally safe for most garden feeding?
Many crops tolerate mid-range root-zone temperatures. Use your crop guide, but avoid extremes. The calculator helps you approach a stable target and reduce sudden swings during watering.
2) Why does warm solution sometimes cause root stress?
Warmer water holds less dissolved oxygen. Low oxygen can stress roots and reduce uptake. If your reservoir runs warm, consider cooling, shading, aeration, or smaller batches.
3) Can I mix two water sources and skip heating equipment?
Often yes. If you have a warm source and a cool source, the ratio mode estimates volumes to hit your target. Always verify the blend temperature before applying.
4) What does the UA value represent?
UA approximates how quickly your tank gains or loses heat to ambient air. Higher UA means faster heat exchange. Use it when your reservoir is exposed to wind, sun, or cold rooms.
5) Why is the time estimate sometimes “unreachable”?
With strong heat loss or limited power, the system can settle at an equilibrium temperature before reaching your target. Lower losses, increase power, or adjust the target closer to ambient.
6) Does this work for nutrient solutions, not just water?
Most dilute nutrient solutions behave close to water for heat calculations. For very concentrated mixes, results remain a good estimate, but confirm with a thermometer and observe plant response.
7) How should I use the CSV and PDF outputs?
Run a calculation, then download a report to log batch volume, temperatures, and estimated energy. This supports repeatable mixing procedures and makes troubleshooting easier when conditions change.