1
GEOTHERMAL SYSTEMS AND
TECHNOLOGIES
1. DIRECT USE OF GEOTHERMAL ENERGY
2 6. DIRECT USE OF GEOTHERMAL ENERGY
Geothermal resources have beenutilized “directly” for centuries.
Direct use means direct utilization ofheat for heating – there are no energyheat for heating – there are no energytransformations in-between.
Direct use resources are tapped for avariety of uses, such are: spaceheating, drying farm and timberproducts, aquaculture and industrialuses.
6.1. Introduction3
The main utilization categories, known as“direct use”:
� swimming, bathing and balneology;� swimming, bathing and balneology;� space heating and cooling, including
district energy systems;� agricultural applications;� industrial applications;� GSHPs.
6.1. Introduction4
The different applications for
direct-use of GE vary according
Examples of direct-use applications for geothermal energy (modified from
Lindal, 1973)
direct-use of GE vary according
to temperature. Direct-use is
typically associated with lower-
temperature – < 150°C GRs.
6.1. Introduction5
Economic, environmental and energy benefits:
� Lower heating costs� Lower heating costs
� Reduced emissions of CO2, NOx, SOx
� Better use of resources
� Domestic
� Minimal ongoing costs after installation
� Unlimited application of GSHPs
6.2. Technologies for direct use
of geothermal energy6
A chain of technologies involved:� Drilling technologies; � Well head completion; � Geothermal water treatment; � Heat exchanger complete;
Geothermal water treatment; � Heat exchanger complete; � Pumping station;� Water transportation; � Heat distribution systems; � Regulation of heat supply;� Systems for collection of
effluent geothermal water; � Re-injection.
6.2. Technologies for direct use of geothermal energy7
The typical equipment for a direct-use system includes: � down hole and circulation pumps,� down hole and circulation pumps,� heat exchangers,� transmission and distribution lines,� heat extraction equipment,� peaking or back-up generators, and� water disposal systems.
Typical direct use geothermal heating system configuration
6.2.1. Heat exchangers (direct or open loop system)8
Normal heat carrier is the thermal water, taken fromthe well.
Using of an open loop geothermal system is possibleonly when the geothermal fluid is not corrosive andUsing of an open loop geothermal system is possibleonly when the geothermal fluid is not corrosive andwith intention to scaling.
Much more convenient are closed loop systems.
The principal heat exchangers used in geothermalsystems are: the plate, shell-and tube, and the down
hole ones.
6.2.1. Heat exchangers (direct or open loop system)9
Gasket plate- and-frame
heat exchanger construction
Flows in plate heat exchanger
6.2.1. Heat exchangers (direct or open loop system)10
Shell-and-Tube Exchangers.
The three most common types
of shell-and-tube exchangers
Shell-and-tube exchanger with one shell pass and one tube pass
of shell-and-tube exchangers
are:
1- fixed tube sheet design,
2- U-tube design, and
3- floating-head type.
11
Typical down-hole heat exchanger (DHE)
system (Klamath Falls, OR).
6.2.2. Heat distribution and piping12
Usually the geothermal well is located somedistance away from the user. Therefore, atransmission pipeline is required to transportthe geothermal fluid.the geothermal fluid.
The cost of transmission lines and thedistribution networks in direct use projects issignificant.
Both metallic and nonmetallic piping can beconsidered for geothermal applications.
6.2.2. Heat distribution and piping13
Carbon steel is now the most widely used material for geothermal transmissionlines and distribution networks.
Corrosion is a major concern with steel piping.
Galvanized steel has been employed with mixed success in geothermal applications.Galvanized steel has been employed with mixed success in geothermal applications.
Aboveground geothermal pipes to the
Nesjavellir geothermal power plant
Buried pre-insulated
pipes for Geothermal
district heating, Xian
Yang – China
6.3. Types of direct use of geothermal energy14
Spas and Pools
The word spa derives from a natural hotspring of iron-bearing water in Belgiumthat was used starting in 1326 to curethat was used starting in 1326 to cureailments.
The hot water from the earth,containing certain minerals can give thespa meaning from a religious, symbolic,aesthetic, philosophical, or medicalcontext.
6.3.1. Spas and pools15
Typical temperature for a swimming pool is27oC, therefore in a geothermal heated pool,the hot water must often be cooled by mixingthe hot water must often be cooled by mixingwith cooler water, aeration, or in a holdingpond.
Geothermally heated swimming pools havealternative energy sources if the geothermalwater is not used directly in the pool.
6.3.2. Domestic water heating16
The various uses for domestic hot water
include dish washing, laundry, bathing and
hand washing. Hot water consumptionhand washing. Hot water consumption
depends on uses and application
temperature.
Domestic hot water heating often requireswater higher temperatures than spaceheating does.
17
The storage recharge
method for DHW
heating
6.3.2. Domestic hot
water heating
Instantaneous method for DHW heating
6.3.3. Swimming pool heating
18
The size of a swimming pool
is important item in the pool
design; it is a basic factor for
Swimming pool heating with
geothermal water
design; it is a basic factor for
determining the pool’s ser-
vice, water value, selection
of equipment etc.
6.3.3. Swimming pool heating19
Heat loss from outdoor pools is mainly due to: convection, evaporation,
radiation, conduction and rain.
With geothermal heat pump systems. Heating swimming pool with geothermalWith geothermal heat pump systems. Heating swimming pool with geothermalheat pump depends on the climate.
In northern climates, more heat is generally extracted from the ground than isrejected during the year.
In southern climates, the opposite occurs and more heat is generally rejected tothe ground than is extracted during the year.
6.3.3. Swimming pool heating
20
Figure illustrates the systemfor Southern climates. The
Swimming pool heating
with geothermal heat pump
for Southern climates. Thevertical bore ground loop wasused for the combined loadsof the house and pool.
6.3.4. Space heating and cooling (air conditioning)21
Under the expression "space air conditioning" both heating and cooling ofrooms is understood.
Space conditioning includes both heating and cooling.
Absorption space cooling with geothermal energy has not been popular becauseAbsorption space cooling with geothermal energy has not been popular becauseof the high temperature requirements and low efficiency.
District heating involves the distribution of heat from a central location, througha network of pipes to individual houses or blocks of buildings.
The distinction between a district heating and space heating system is thatspace heating usually involves one geothermal well per structure.
6.3.4. Space heating and cooling (air conditioning)22
Thermal load density or heat demand. High heat density is recommended.Geothermal can usually meet 50% of the load 80 to 90% of the time, thusimproving the efficiency and economics of the system. Fossil fuel peaking usuallyapplied.applied.
Geothermal district heating systems are capital intensive. The typical savings toconsumers range from approximately 30 to 50% per year of the cost of natural gas.
Heating of individual rooms and buildings is achieved by passing geothermal water(or secondary fluid) through heat convectors (or emitters). The method is similar tothe one used in conventional space heating systems.
6.3.4. Space heating and cooling (air conditioning)23
Three major types of heat convectors are used for space heating:
1. forced convection systems2. natural convection systems3. radiant panels3. radiant panels
Forced convection air systems are based on the use of a water/air heat exchangerthrough which the air is blown by a fan.
Main characteristics of space heating:
� Preferred water temperatures 60-90°C. Common return water temp. is 25-40°C.� Chemical composition of the water is important.� Radiators or floor heating systems and air heating systems.� GHP can be used if the temp. of the resource is too low for direct application.
6.3.4. Space heating and cooling (air conditioning)24
The supply temperatures required for a range of domestic heating distribution systems:
Distribution systemDelivery
temp. °C
Under floor heating 30-45Under floor heating 30-45
Low temperature radiators 45-55
Conventional radiators 60-90
Air 30-50
GSHP systems may not be suitable for direct replacement of conventional water-based central heating systems.
6.3.4. Space heating and cooling (air conditioning)25
Wet radiator system operates at 60°C to 80°C - drop in circulating temp.by 20°C → increase in emitter surface by 30% to 40%.
Air system - delivery temperature of 35°C → increase of the air changeAir system - delivery temperature of 35°C → increase of the air changerate by up to three times to maintain the same output.
Under floor heating is the most efficient with a GSHP system.
Fan convectors are possible, but necessary flow temperatures of ̴ 50°Creduce the system efficiency.
Heating elements26
Natural air convection systems.
The air flow through the heating element as a result of different density between hot and cold air.
Pipes. The simplest system is the
Convectors. They have much largerheating surface per unit length of pipe,but they show weak performance whenheating fluids with lower temps are used.
Pipes heating element
Pipes. The simplest system is the use of pipes as heating elements.
Different types of heating elementsa-fan coil; b-convector; c-radiator; d-floor heating
27
Heating elements
Convector in the wall construction with the masks on the front side
Cast iron radiator
Heating elements28
Radiant panel systems, involve circulation ofwarm water (35-45°C) through piping that isembedded in the floor of the building.
Older systems were constructed with copper orsteel piping.Older systems were constructed with copper orsteel piping.
The new, nonmetallic piping products forradiant panel systems, made this systemswidely applicable now-a-days.
The combination of geothermal and radiantfloor heating results in a system that has thebenefits of both technologies independentlyand some distinct advantages.
Radiant floor heating system
Heating elements29
Forced air convection systems - water/air heat
exchanger through which the air is blown by a fan.
Fan coil units. The fan coil units themselves are
comprised of a finned-tube coil, an insulated drain pan
Fan coil unit
comprised of a finned-tube coil, an insulated drain pan
under the coil to collect condensate, a fan to move air
through the coil, filters, control valve, and a cabinet to
house these components. Typically fan coils are either
located above ceilings or ducted to ceiling diffusers, or
under windows using console units. Console units are
sometimes ducted through the wall for ventilation air.
Heating elements30
A two-pipe fan coil system consists of fancoil units with single coils - connected totwo pipes (one supply pipe and one returnpipe) that either provide hot water orpipe) that either provide hot water orchilled water throughout the building.
Fan heaters. Fan heaters are normally usedfor permanent heating of ware-houses,industrial premises, work-shops, sportshalls, shops and the like.
FHW fan heater with water coil
Heating elements31
Air handling units. When more rooms in abuilding and in industry need airconditioning, centralized air conditioningconditioning, centralized air conditioningunit is necessary.
Air conditioning is done for comfort orindustrial purposes. “Comfort airconditioning” is the conditioning of air toachieve such an environment. Central air handling unit for a
building with more rooms
District heating systems32
District heating originates from acentral location, and supplies hotwater or steam through a network ofpipes to individual dwellings or blockspipes to individual dwellings or blocksof buildings.
A geothermal well field is the primarysource of heat. Depending on the GWquality: open and closed loop systems.
Closed loop double pipe geothermal district heating system
District heating systems33
GDHS are in operation in at least 12countries. The Reykjavik, Iceland,district heating system supplies heatfor around 190,000 inhabitants. The
Reykjavik district heating system (prior to the Nesjavellir connection)
district heating system supplies heatfor around 190,000 inhabitants. Theinstalled capacity is 830 MWt - to meetthe heating load to about -10oC; duringcolder periods, the increased load ismet by large storage tanks and an oil-fired booster station.
District heating systems34
In France, production wells in sedimentary basins providedirect heat to more than 500,000 people in 170,000dwellings from 34 projects with an installed capacity of243 MWt and annual energy use of 4,030 TJ/yr.
These wells provide from 40 to 100oC water from depths
Melun l’Almont (Paris) doublet heating system [22]
These wells provide from 40 to 100oC water from depthsof 1,500 to 2,000 m.
The GW with 70oC is removed from production well. Aftercooling in heat exchangers for space heating and DHW,the water with temp. of 35oC, is injected back throughreinjection well.
District heating systems35
Space conditioning includes both heatingand cooling.
Approx. 62,000 m2 are heated with GWfrom 3 wells at 89oC. Up to 62 l/s of fluid
Oregon Institute of Technology heating and cooling system
from 3 wells at 89oC. Up to 62 l/s of fluidcan be provided to the campus, with theaverage heat utilization rate over 0.53MWt and the peak at 5.6 MWt.
In addition, a 541 kW chiller requiring upto 38 l/s of geothermal fluid produces 23l/s of chilled fluid at 7oC to meet thecampus cooling base load.
District heating systems36
Geothermal district heating systems are capital intensive.
The main costs are: initial investment costs, for production and injection wells,down-hole and transmission pumps, pipelines and distribution networks,monitoring and control equipment, peaking stations and storage tanks.monitoring and control equipment, peaking stations and storage tanks.
Operating expenses are comparatively lower than in conventional systems.
Some economic benefit can be achieved by combining heating and cooling inareas where the climate permits.
The load factor in a system with combined heating and cooling would be higherthan the factor for heating alone, and the unit energy price would consequentlyimprove.
37
In indirect central heating systems, GWat the exit of flat plate heat exchangermay have a temperature between 40 to45oC. Waste GW at this temperature canbe used for heating of domestic water,
District heating systems
District heating and domestic hot water preparation in the city Zijinxinli in the province Tianjun in China
(200,000 inhabitants)
45 C. Waste GW at this temperature canbe used for heating of domestic water,or as a heat source for GHP which heatsthe water for central heating.
38
The central geothermal heating plant,where the return water from the heatingelements ∼45°C is used as a heat sourcefor a GHP. The heat pump increases thewater temp. to ∼60oC, which is then used
District heating systems
District heating with geothermal water and geothermal heat pump
∼
for a GHP. The heat pump increases thewater temp. to ∼60oC, which is then usedfor heating.From the flat plate heat exchanger GW of30-32°C with circulating pump is injectedin the second well.From fan coil units, the water with 45°Centers to the evaporator of the heat pumpto evaporate the refrigerant working fluid.
District heating systems39
Space cooling is a feasible option where absorption plants can be adapted to
geothermal use. The technology is well known, and they are readily available on
the market. The absorption cycle is a process that utilizes heat instead of electricity
as energy source.as energy source.
The refrigeration effect is obtained by utilizing two fluids: a refrigerant, which
circulates, evaporates and condenses, and a secondary fluid or absorbent.
For applications above 0°C, the cycle uses lithium bromide as the absorbent and
water as the refrigerant.
For applications below 0°C an ammonia/water cycle is adopted, with ammonia as
the refrigerant and water as the absorbent.
Geothermal fluids provide the thermal energy to drive these machines.
Refrigeration40
Cooling can be accomplished from geothermal energy using lithium bromide andammonia absorption refrigeration systems.
The major application of lithium bromide units is for the supply of chilled waterfor space and process cooling.
∼
for space and process cooling.
They may be either one- or two-stage units.
The two-stage units require higher temperatures (∼160°C); but, they also havehigh efficiency.
The single-stage units can be driven with hot water at temperatures as low as77°C.
The lower the temperature of the geothermal water, the higher the flow raterequired and the lower the efficiency.
Refrigeration41
Some of the geothermal uses may notpromise an attractive ROI due to the highinitial capital cost.
Refrigeration as a part of geothermal district heating system (cascade use of heat)
initial capital cost.
Cascading or waste heat utilization.
Combined heat and power application.
6.3.5. Agribusiness applications42
Agribusiness applications (agriculture and aquaculture) are particularly attractive.
A number of agribusiness applications can be considered:
� greenhouse heating,
� aquaculture and animal husbandry facilities heating,� aquaculture and animal husbandry facilities heating,
� soil warming and irrigation,
� mushroom culture heating and cooling, and
� bio-gas generation.
Up to 35% of the product cost.
The agricultural applications of geothermal fluids consist of open-field agriculture
and greenhouse heating. Thermal water can be used in open-field agriculture to
irrigate and/or heat the soil.
Heating greenhouses with geothermal energy43
The most common application of geothermal energy in agriculture is for
greenhouse heating. Construction may be considered to fall into one of the four
categories: glass, plastic film, fiberglass or similar rigid plastics and combinations.
Glass greenhouses are the most expensive to construct.Glass greenhouses are the most expensive to construct.
In many cases, fiberglass panels are employed on the side and end walls of the
structure.
Plastic film greenhouses are the newest variation in greenhouse construction
techniques.
Heat loss of the fiberglass house is about the same as the glass house.
Heating greenhouses with geothermal energy44
Heating systems in geothermal greenhouses.Heating installations with natural
convection: a-aerial pipe heating; b-benchconvection: a-aerial pipe heating; b-benchheating; c-low position heating pipes foraerial heating; d-soil heating.Heating installations with forced convection:
e-lateral position; f-aerial fan; g-highposition ducts; h-low-position ducts.
Heating greenhouses with geothermal energy45
Heating requirements. In order to select a heating system for a greenhouse, the
first step is to determine the peak heating requirement for the structure. Heat loss
for a greenhouse is composed of two components:
(a) transmission loss, and(a) transmission loss, and
(b) infiltration and ventilation losses.
The heat exchanger is placed
between two circulating loops, the
geothermal loop and the clean loop.
Heat exchanger schematic
Heating greenhouses with geothermal energy46
There are basically six different geothermal heating units applied to greenhouses:finned pipe, standard unit heaters, low-temperature unit heaters, fan coil units,
soil heating and bare tube.
The heating systems can be classified according to theThe heating systems can be classified according to theposition of the heating installation:
1. Heating systems in the soil;2. Heating systems laid on the soil surface or on the benches;3. Aerial heating systems;4. Cascading;5. Combinations of the above.
Heating greenhouses with geothermal energy47
Aerial heating systems. The pipes can besmooth or finned steel pipes or smoothsmooth or finned steel pipes or smoothplastic pipes which are placed along thelength of plant rows, along the side wallsunder the roof or below the cultivationbenches.
The temperature of the geothermal watershould be above 60°C.
Aerial pipe heating system
Heating greenhouses with geothermal energy48
Soil heating. In this system the soil is used asa large radiator. The tubes are buried in thesoil.soil.
This system creates very even temperaturedistribution from floor to ceiling and does notobstruct floor space or cause shadows
Soil heating system (pipes are buried in the soil)
Heating greenhouses with geothermal energy49
Heating systems laid on soil surface or on the benches.
Soil heating system (pipes are placed on the soil)
Soft plastic bags with holes for allocation of plants
Heating greenhouses with geothermal energy50
Type of heating elements of the vegetative heating system
a - parallel pipes positioned along the plants rows;
b - pipes positioned bellow the growing pots row;
c - soft plastic tubes positioned in parallel with the plant c - soft plastic tubes positioned in parallel with the plant
rows;
d - the same but with prefabricated connected poly-pipe
lines;
e - rigid plastic plates with channels for heating fluid flow;
f - soft plastic tubes with holes for allocation of plants
Heating greenhouses with geothermal energy51
Forced air heaters
The two main categories are the unitheaters and the fan coil units.
The standard installation of unit heatersThe standard installation of unit heatersconsists of hanging the unit at one end ofthe structure and discharging the supply airtoward the opposite end.
In longer houses (>38 m), it is advisable toinstall units at both ends to assure heatdistribution.
Typical unit heaters installation
Heating greenhouses with geothermal energy52
Cascading. This heating system is appliedonly in double layered constructions and iscommon in cheap plastic greenhouses.It is effective as a heating method, but hasIt is effective as a heating method, but hasa lot of disadvantages and is not widelyapplicable.
Combination. A combination of differentheating systems is necessary in coldclimates.
Cascading greenhouse heating
Heating greenhouses with geothermal energy53
Various solutions are available in
achieving optimum growth conditions.
The walls of the greenhouse can be made
Growth curves for some crops.
The walls of the greenhouse can be made
of glass, fiberglass, rigid plastic panels or
plastic film.
Geothermal heating of greenhouses can
considerably reduce their operating
costs, which in some cases account for
35% of the product costs.
Farm animals54
Industrial farm animal production - all
aspects of breeding, feeding, raising, and
processing animals or their products for
human consumption.
Effect of temperature on growth or production of food animals.
In many cases geothermal waters could beused profitably in a combination of animal
husbandry and geothermal greenhouses.
The energy required to heat a breedinginstallation is about 50% of that requiredfor a greenhouse of the same surface area.
Aquaculture55
Species
Tolerable
Extremes
(oC)
Optimum
Growth
Growth period
to market size
(months)
Temperature of water determines which species can be grown
The temperatures required for (oC) (months)
Lobsters 0-31 22-24 24
Salmon
(Pacific)4.5-25 15 6-12
Catfish 1.7-35 28-30,6 6-24
Tilapia 8.4-41 22.2-30 12
Trout 0-31.7 17,3 6-8
Shrimp 4.5-40 23.9-30.6 6-8
The temperatures required for
aquatic species are generally in
the 20-30°C range.
Increased growth rates by 50
to 100%.
Aquaculture56
Geothermal heated pond for fish farming on Lower Klamath Lake Road.
Geothermal heated pond for alligator farming in Colorado.
Aquaculture57
Microalgae cultivation is based upon the logic of the photosynthetic process: solar energy is used for the synthesis of organic compounds out of non-organic synthesis of organic compounds out of non-organic substances.Different methods of algal production technology optimization by geothermal energy consist of:� use of geothermal CO2 and energy for optimizing
photosynthesis.� use of geothermal water for nutrition algal media
preparation.� use of geothermal energy for algal biomass drying
Open air algae cultivation in Israel
6.3.6. Industrial applications58
The different possible forms of utilization of geothermal fluids (steam or water),include:
� Drying- the most common operation;� Process heating–preheating of boiler water etc.;� Process heating–preheating of boiler water etc.;� Evaporation–extraction of salt;� Distillation–liquor and hydrocarbon industry;� Washing–food industry;� Chemical extraction–gold separation from ores;� Pasteurization of milk;� De-icing;� Refrigeration–absorption freezing (lithium-bromide and ammonia).
6.3.6. Industrial applications
59
180°C Evaporation of highly concentrated
solutions, Refrigeration by ammonia
absorption Digestion in paper pulp.
170°C Heavy water via hydrogen sulfide
process. Drying of diatomaceous earth.
160°C Drying of fish meal. Drying of timber.
100°C Drying of organic materials. Seaweed,
grass. vegetables etc. Washing and
drying of wool.
90°C Drying of stock fish. Intense de-icing
operations.
80°C Space-heating (buildings and green-
Several reports have been written in the past to identify sectors where geothermal heat
could play a role. Such studies have been made by Lindal, Reistad, Howard and Lienau.
160°C Drying of fish meal. Drying of timber.
150°C Alumina via Bayer's process.
140°C Drying farm products at high rates. Food
canning.
130°C Evaporation in sugar refining. Extraction
of salts by evaporation and crystal-
lization. Fresh water by distillation.
120°C Most multi-effect evaporation.
Concentration of saline solution.
110°C Drying and curing of light aggregate
cement slabs.
80°C Space-heating (buildings and green-
houses).
70°C Refrigeration(lower temperature limit)
60°C Animal husbandry. Greenhouses by
combined space and hotbed heating
50°C Mushroom growing. Balneology.
40°C Soil warming Swimming pools,
biodegradation. Fermentations.
30°C Warm water for year-round mining in
cold climates. De-icing. Fish hatching.
20°C Fish farming.
Industrial drying and dehydration60
Batch – tunnel dryer.Uses fairly low temp. hot air from 38 to105oC.
Using a 7oC min. approach temperaturebetween the geothermal fluid andprocess air, a well with 110oC fluid isrequired. The first-stage air temp. canbe as low as 82oC; however,temperatures >93oC are desirable.
The construction of the rack
drying cabinet
Industrial drying and dehydration61
Continuous - Conveyor Belt Dryer. Various vegetable and fruit products are feasiblewith continuous belt conveyors or batch (truck) dryers with air temperatures from40o to 100oC.
Continuous belt dehydration plant
Industrial drying and dehydration62
Grain drying. Significant amounts of energyare consumed annually for grain drying and
Perforated false floor system for bin drying of grain
are consumed annually for grain drying andbarley malting. These processes can be easilyadapted to geothermal energy in thetemperature range of 38 to 82oC.
Industrial drying and dehydration63
The equipment does not use a drying belt.
The only moving part is the air blower.
The air blower is placed at one side of the
3D view design of the geothermal batch dryer for drying grains and beams
The air blower is placed at one side of theheat exchanger while the drying room is onthe other side.
The drying duration depends on the originalhumidity of the products.
Industrial drying and dehydration64
Drying rice is probably the most difficult toprocess without quality loss. Rice withmoisture content > 13.5% cannot be safely
A schematic flow diagram of the geothermal rice drying plant in Kocani, Macedonia
moisture content > 13.5% cannot be safelystored for long periods. It is harvested at amoisture content of 20 to 26%, and dryingmust be started promptly to prevent therice from souring.
Industrial drying and dehydration65
Drying Lumber. Moisture occurs in wood incell cavities and in the cell walls. The majorityof the moisture is first lost from the cavities.In the kiln drying process, the evaporationIn the kiln drying process, the evaporationrate must be carefully controlled to preventthe stresses that cause warping.
Kiln drying is usually carried out as a batchprocess. The kiln is a box-shaped room withloading doors at one end.
Long shaft double-track compartment kiln with alternately opposing internal fans
Dairy processing66
Milk starts to go bad within hours after milking. The major methods of treatment are:
chilling, heat treatment and evaporation.
Thermal treatment involves heating every milk particle or a milk product to a specific
temperature for a specific period of time without allowing recontamination during thetemperature for a specific period of time without allowing recontamination during the
heat treatment process.Process Temp.(°C) Time (s)
Thermisation 63-65 15
LTLT pasteurization of milk 63 1800
HTST pasteurization of milk 72-75 15-20
HTST pasteurization of cream >80 1-5
Ultra pasteurisation 125-138 2-4
UHT (flow sterilisation) 135-140 1-3
Sterilisation in container 115-120 1200-1800
The main categories of heat
treatment in dairy processing
Snow melting67
Geothermal heating of roads and pavements
A pavement in Klamath Falls with snow melting installation
6.3.6.3. Snow melting68
Geothermal energy can be supplied to the system by one of the three methods:
� directly from a well to the circulating pipes;� through a heat exchanger at the well head;� by allowing the water to flow directly over the pavement� by allowing the water to flow directly over the pavement
The work of the system is normally regulated by a computerized control system. Itcontinuously receives information from various sensors and automaticallyactivates the heating cycle when certain conditions are met.