Temperature control equipment

For several years now, the constant drive to improve wine quality has led wineries to install temperature control equipment.
Temperature control does not create new conditions for winemaking or maturing wines: it simply reproduces their best aspects.
From the grape to the glass, at every stage in its life, each wine must be prepared, vinified, stabilised and consumed at an optimum temperature with relatively small acceptable variations. At each stage of the winemaking process, this ideal temperature helps to improve the various aspects of the wine's quality.

Development of grape and fermentation aromas.
Clarification of musts and wines.
Optimum development and inhibition of yeasts and bacteria.
Extraction of skin compounds: tannins, anthocyanins, aromas.
Optimisation of oxidation-reduction and esterification phenomena.
Development of olfactory and gustatory characteristics

Outside winery

In most cases, good temperature control also makes it possible to optimise the use of vinification vats as well as wine ageing or bottle storage rooms.

Technical presentation

Each oenological operation must be carried out at a precise temperature in very variable climatic or practical conditions (premises).

Equipment selection strategy

Defining the temperature control system best suited to a given production unit requires a whole series of technical, economic and practical parameters to be taken into account. To do this, a case-by-case study should be carried out with a professional, taking into account the following factors:

Overall heat balance for the farm (heat output and heat exchanger surface area)
Choice of energy (electricity, gas, fuel oil)
Choice of heat transfer fluid (water, brine)
Level of control required (manual, semi-automatic, automatic)
Choice of components based on reliability
Quality of after-sales service
Installation and running costs

Different types of temperature control equipment

wine coolers and heaters
heat treatment tanks
external heat exchangers
internal" and "belt" heat exchangers
cooling tower
the gas heater
the immersion heater
cO2 in the form of ice or snow
vortex tubes
cold or hot air generators
other heat treatment systems

Which system should you choose? Carrying out a heat balance

Before choosing a heat treatment system, it is important to accurately assess the cooling and heating capacity requirements of the winery.

The cellar heat balance is an assessment of the heating and cooling capacity, tank by tank, day by day, required to achieve the best thermal conditions chosen by the winemaker for each oenological operation.

The power to be installed can vary greatly from one winery to another, and depends on a wide range of factors:

Type of grape: white, red or both
Oenological operations to be carried out
Daily input rate
Vat materials and volumes
Total volume vinified and volume per unit operation
Duration of each operation and daily use of machinery
Ambient temperatures (hot or cold years) or desired temperatures.

All these parameters must therefore be taken into account when establishing a cellar heat balance worthy of the name. Global estimates, based solely on the volume of the harvest, can satisfy neither a winemaker's concern for quality nor for sound management.

Find out more about the " Heat balance " module.

Following several years of observations, measurements and practical studies, we can propose a general method that can be adapted to each case. The questions that need to be answered are those that perfectly define the problems to be solved and enable the user to objectively compare and choose the solution best suited to his winery:

What is the harvest schedule?
What are the characteristics of the vat room?
What are the heating requirements?
What thermal equipment is available or can be provided?

Operation and implementation of an installation

Before the installation is commissioned, it must be approved in the same way as a building or a house. Each component installed must correspond to the initial proposal, which will have been validated by a design office or consultancy body.

Hydraulic systems must be rinsed before use to remove any metal or plastic residues that could cause the system to malfunction. They are then bled to remove any air residues contained in the system.
The networks must then be pressure tested, at around 2 bars above the operating pressure. This operation checks that there are no potential leaks. It must be carried out before any insulation, which could mask a possible leak and eventually damage the insulating material or other parts of the installation (corrosion, dirt).

If necessary, the water used in the circuits should be treated for limescale and iron, to prevent deterioration of the network and slow down any drop in exchanger performance.
All system components (pumps, piping, hoses, valves, solenoid valves, fittings, etc.) must be able to withstand water temperatures of 5 to 70°C, condensation and SO2 vapours over the long term without damage or corrosion.

Initial start-up must be carried out by the installer. The installer must supply all the documentation for the appliances, as well as a manual for commissioning and using the system.
It is also advisable to include a contract for the annual re-commissioning of the system, including all the necessary checks (purging, watering, pressure testing, sensor calibration, start-up, etc.).

The system should also be designed so that users with the necessary skills can carry out standard replacement of certain parts themselves (solenoid valves, regulators, sensors). These components must be easily accessible. A set of spare parts can be supplied with the installation.

Hygiene

Before and after each use, all heat exchangers in contact with must, grapes and wine must be cleaned, disinfected and rinsed with water and products suitable for oenology, in compliance with the recommendations of each manufacturer and the regulations. Heat exchangers are subject to temperature differentials and scale build-up very quickly.

The usual cleaning method is the same as that used for descaling stainless steel tanks. For internal or "belt" heat exchangers, it should be carried out as soon as the tank is drained and, if possible, after applying a "thermal shock" by circulating very hot water (70-80°C) through the exchanger. This operation removes the fresh scale from the exchanger. For external exchangers, the complete heat treatment circuit is used, with circulation of descaling liquid and then disinfectant in an open or closed circuit, followed by vigorous rinsing. Hot water, with an outlet temperature of at least 80°C, is also very effective for removing scale before using a chemical method.
The operation must be rigorous.

Environment and regulations

The refrigeration industry is currently undergoing major upheaval as CFCs are phased out and HCFCs (R22), which are currently widely used in cooling units in wineries, are gradually replaced. This replacement will take place until 2013, when HCFC production must be stopped and replaced by fluids considered less polluting (ammonia, HFC, CO2, H2O).

On the other hand, installations still running on CFCs (R12 or R502) need to be replaced quickly, as production of these fluids is now banned, making it extremely difficult to obtain them in the event of a loss at the installation.
It would already seem advisable to install units compatible with these replacement fluids (R134A, R407A, B and C, R507, R410A).

Safety

Temperature-control equipment is subject to the general rules governing the compliance of cellar equipment. It is essential that the entire electrical supply is protected in accordance with current regulations and that each component of the installation (from production to regulation) has CE certification on the equipment and the user manual.

Components of temperature control systems

Temperature control systems, which are highly scalable, are made up of different modules to ensure a high degree of versatility in thermal operations on the one hand, and better monitoring of the processes in progress on the other.
The operating principle involves producing a heat transfer fluid (hot or cold) which is then distributed to individual heat exchangers. Each heat exchanger has its own manual or automatic control.
Automatic control can be provided by temperature regulators, a PLC or a microcomputer.

Thermal energy production

This is provided either by a chiller , the operation of which is detailed in the technical presentation in the "Cooling production" section, or by a boiler, the operation of which is detailed in the technical presentation in the "Heating production" section.

Distribution

The treated fluid is sent by a pump to various storage, circulation or intermediate exchange elements, then to the exchangers.

Find out more about the " Fluid distribution " module.

Controls

The fluid must only circulate in the exchangers when necessary. Each exchanger is therefore fitted with a system of manual or automatic valves. In the case of automatic systems, the temperature is controlled by a sensor and an electronic device that automatically starts or stops the circulation of the fluid depending on the desired temperature.

Find out more about the " Regulation and control systems " module.

Regulation and control

These are electronic devices which centralise the information from the sensors and send orders to the control units. In fact, this is the control panel for the entire installation. Find out more about the "Regulation and control units" module.

Heat exchangers

These are the devices which are in direct contact with the must, grapes or wine and through which the cold or hot fluids from the general distribution system circulate.
These modules are described in detail in the "Equipment" chapters "EXTERNAL EXCHANGERS" and "INTERNAL EXCHANGERS, belts and double envelopes".

Heat production

The 2 types of equipment are :

oil and gas boilers
electric heaters

The initial start-up of an electric, gas or oil-fired boiler can only be carried out by a specialist company. This company must provide the user with all the recommendations for restarting, using and shutting down the boiler in the form of a user manual. However, a wintering and restarting contract can be signed with the company.

The choice of the heat output to be installed should be based primarily on the heat balance. This capacity (once determined) must be based on :

The desired water temperature (water or brine)
Energy (electric, gas, oil)

Comparatif pouvoirs calorifiques des energies

This table compares the heat output of the different energy sources.

This table contains the main characteristics to be found on a boiler's documentation.

Other criteria that can be taken into account to guide the choice of energy :

Locally available fuel, with the distance from supply sources posing problems such as cost, which increases with transport costs, storage management and capacity..
Importance of investment and financing capacity.
Proposed supply contracts.
Price of fuel, subscription, meter hire, tank hire, etc
Guarantee of supply, quantity, quality, etc
Possibility of contract revision.

Notions of cost

Once the heat balance has been established, you can estimate the amount of heat energy consumed during the winemaking process. To do this, simply multiply the daily hourly output by 24 and divide this quantity of energy by the boiler efficiency (ratio of heat output to power input (called C.O.P. for chillers)). This gives the estimated kW/h consumed per day and therefore the operating cost.

Refrigeration production

The 2 types of equipment are

Electric chillers
Gas chillers

Installation

The initial start-up of an electric or gas chiller can only be carried out by a specialist company. This company must provide the user with all the recommendations for restarting, using and stopping the chiller in the form of a user manual. However, a wintering and restarting contract can be signed with the company.

Choice of equipment

The choice of the cooling capacity to be installed should be based primarily on the heat balance. This capacity (once determined) must be based on :

The desired water temperature (chilled water or brine)
The outside air temperature
The energy (electricity, gas) and fluid used (R22, R407, R134a, ammonia)

Caracteristiques principales d'une documentation de groupe de froid

Main characteristics found on the documentation for an electric chiller

Malfunctions

Electric chillers are generally fitted with indicators or lights to monitor their operation.
Discharge pressure (H.P. indicator or light)
This is analysed by a pressure switch which controls the efficiency of the condensation process. Any loss of efficiency leading to a rise in pressure is due to :

Dirty tubes in the condenser
Reduced air flow (fan failure) or water on the condenser or externally dirty coil.

The pressure at which the refrigerant evaporates (B.P. or L.P. indicator or sight glass)
This is controlled by a B.P. pressure switch. Too low a pressure is due to :

A lack of refrigerant
Faulty expansion valve
A blocked dehydrator
A defective capacity reduction device.

The temperature of the fluid leaving the evaporator (temperature indicator or sight glass)
This is measured by a low temperature thermostat. The main reasons for a low water temperature are as follows:

Reduced water flow (pump failure)
A water outlet set point that is too low.

Effective compressor pressure
This is measured by an oil pressure switch which gives the difference between the oil pressure in the lubrication circuit and the suction crankcase pressure. Any drop in oil pressure can be caused by :

Lack of oil
A faulty oil pump
Destroyed oil resistance promoting condensation of the coolant in the oil.

These are just some of the faults that can affect a refrigeration unit. The aim of this paragraph is above all to familiarise the user with the operation of a refrigeration unit, to provide the necessary information to analyse a problem accurately and to enable the after-sales service to intervene more effectively.

Cost concepts

Once the heat balance has been established, it is possible to estimate the amount of cooling and heating energy consumed during the winemaking process.
To do this, simply multiply the daily hourly power by 24 and divide this amount of energy by the C.O.P. (Ratio of cooling power to power input (called efficiency for boilers). of the cooling unit. This gives the estimated kW/h consumed per day and therefore the running cost.

Oenological practices: focus on thermal aspects

Summary of the thermal cycles for the different vinifications

Cycle thermique de la vinification blanc sec

Thermal cycle for "Dry white" vinification

Cycle thermique de la vinification blanc liquoreux

Thermal cycle for "Sweet white" vinification

Thermal cycle for "Rosé and Clairet" vinification

Cycle thermique de la vinification rouge

Cold storage for 15 to 20 days at around -5°C, sometimes with intermediate filtration.
Contact" treatment for a few hours at around 0°C, with mass seeding with micronised potassium bitartrate.
Continuous treatment, in a few tens of minutes, at around 0/-5°C, with or without inoculation, using specialised equipment.

In most cases, cooling must be rapid - from a few seconds to a few hours - but with flow rates that can be moderate because the possible treatment period is relatively long (several weeks or months a year).

Some oenological aspects

The success of these treatments requires rigorous oenological control (stability tests, saturation temperature, mini-contact, etc.) before and after treatment.
All the traditional oenological parameters (oxidation, SO2, CO2, etc.) must be controlled to ensure that the organoleptic qualities of the wines are fully respected.
It is well suited to red wines, where it also stabilises the colouring matter.
Benefits of applying it to young wines:

more effective (over-saturation)
gives the wine time to "recover" from the treatment

Ageing and conservation of wines

Principle

Wine maturing and conservation are sensitive to temperature conditions; high temperatures accelerate biochemical processes that are slowed down by lower temperatures. Optimum values vary greatly depending on the wine and the way it is marketed.

Thermal constraints

Wine maturing (in vats or barrels) often benefits from temperatures that vary, but not excessively, over the course of the year, for example between around 5 and 20°C. Constant temperatures slow down the maturing process.

Bottled wines benefit from the opposite conditions: temperatures that are as stable as possible, e.g. between 10 and 15°C, while avoiding values that are too low and could even freeze (e.g. January 1985) or too high, exceeding 18-20°C.

Temperature control always starts with adequate insulation of the premises. Ventilation, airing and air-conditioning of the winery require serious thought. These two environmental factors, temperature and humidity, are practically always inseparable and must be respected simultaneously. Their importance varies depending on whether the wine is stored in vats, bottles or barrels.

Although we currently have a great deal of high-performance thermal equipment, our knowledge of oenology in this area is very limited and deserves to be studied in greater depth.

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