Geothermal heat exchanger

Posted on December 7th, 2010 by admin
Filed under Geothermal Heating and Cooling | 1 Comment

Geothermal heat exchanger is an essential part of a total geothermal heating system, just as important as the heat pump. Learn how earth thermal energy is delivered to the heat pump using geothermal heat exchanger coils, loops, etc. Geothermal heat exchanger is usually made of PVC shell and flexi-metal base, and is filled with special anti-freeze liquid which. A water pump circulates the heat exchanger liquid through the loops, delivering constant thermal energy from the ground and increasing the efficiency of the geothermal heat pumps.

Geothermal Heat Exchanger

There are two major types of geothermal ground heat exchangers: horizontal and vertical. Horizontal ground heat exchanger means that the pipes are buried in the ground in trenches. There can be single or multiple layers of pipe in the trench, depending on their depths, or the pipe can be buried forming so-called slinky. In cases of multiple layers or slinky we have to keep in mind to allow enough soil between layers or otherwise pipes can interfere in terms of thermal conductivity reducing overall system performance. Vertical ground heat exchanger means that pipes are buried in one or more vertical boreholes that can be 100-500 feet deep.

The choice of whether to use vertical or horizontal heat exchanger depends on available land area, local soil characteristics and drilling costs. For residential applications horizontal systems are usually used. Vertical systems are used in large commercial applications or where land area is limited. In some cases it can be the only choice. In any way the selection between vertical or horizontal geothermal ground heat exchanger should be done after the cost study has been made. The cost study should be performed by the certified contractor. The contractor should also pick out the geothermal equipment which they have experience and are comfortable working with.

The geothermal ground heat exchanger can also be either series or parallel. In series ground heat exchanger system fluid cam only flow in one path and in parallel there can be more low paths in the circuit. There is a list of advantages and disadvantages of each system, and the choice depends on what are you aiming for.

Series system advantages:

1. single flow path and pipe size – meaning that the flow path is well defined which makes removing of the trapped air much easier
2. slightly higher performance – since series system requires larger size pipes there is a better thermal conductivity per square foot of pipe

Series system disadvantages:

1. larger pipe size requires larger volume of antifreeze
2. larger size pipes are usually more expensive
3. increased installation cost
4. limited piping lengths due to the pressure drop characteristics

Parallel system advantages:

1. lower pipe cost because of the smaller diameter
2. lower volume of antifreeze is required
3. lower installation cost

Parallel system disadvantages:

1. special attention is required to assure air removal
2. flow balancing between each parallel path to result in equal lengths loops.

There are major components in geothermal ground heat exchangers:

Supply and return headers –

Supply and return headers are the antifreeze supply and return lines from the geothermal heat pump to the ground loops (ground heat exchanger). They carry out the total system flow of the heat pump system. Headers are constructed from the large diameter pipes to minimize antifreeze flow pressure drop down the length of the pipe run.

Loops –

Loops are the pipes extended from the header down to the borehole or to the trench, returned in the same trench or borehole and joined together to the return header.

Reverse return –

Reverse return is a piping arrangement that allows each loop of a parallel system to have the same inlet and outlet pressure. It is used to cancel out the effects of the pressure drop along the header lines.

U-bend –

U-bend is a 180 degree fitting is a loop type heat exchanger used at the bottom of a borehole or at the end of the trench to return the antifreeze.

Additional Information

Geothermal Heat Pump – the ground source heat exchanger and the heat pump need each other to operate, as one will be useless without the other.

Geothermal heating and cooling system is comprised of heat exchanger, heat pump and distribution system – air ducts or radiant heating pipes.

Geothermal overview

Posted on December 7th, 2010 by admin
Filed under Geothermal Energy | 1 Comment

Pros and cons of geothermal energy: Geothermal energy (also know as ground source, geoexchange or renewable energy) is energy taken from earth, and used to heat or cool buildings depending on season. The basic principle is that in the certain depth in the ground the temperatures are the same throughout the year (about 55 degrees F in New England area) thus giving possibility to retrieve heat during winter time or cold during summer using specific devices called heat pumps. Even though geothermal exchange principle has been known for decades, in residential applications it is relatively new and very fast growing. Geothermal (or ground source heat pump) system can be installed in any residential structure giving its owner the following benefits: 1. Economic – since the […]

How heat pump works

Posted on December 7th, 2010 by admin
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Discover the principal of heat pump operation and what makes a geothermal heat pump so energy efficient. How Heat Pump Works The exchange of energy in geothermal system is done by the heat pump – the device that works similar to the refrigerator. The heat pumps, refrigerators and air conditioners all work in the same manner: by pumping the refrigerant through a closed loop (ground loop in geothermal systems), that has two distinct temperature zones – cold and hot. There a few thermodynamic principles that are used in heat pump’s work. First of all the heat always flows from higher temperature zone to the lower. The heat pump reverses this natural flow making the heat flow from the lower temperature zone to the higher, and […]

Heat pumps

Posted on December 7th, 2010 by admin
Filed under Geothermal Heating and Cooling | 2 Comments

Heat pump basics – learn about heat pump principals: Ground source (geothermal) heat pumps are electrically powered systems that can provide cooling, heating and hot water much more efficiently and less expensively than conventional heating and air-conditioning technologies using ground’s relatively constant temperature. There are two main categories of ground source heat pumps – open loop, and close loop, but major part of all household installations is the closed loop system. The closed loop geothermal heating system circulates the water-based antifreeze solution through a series of pipes buried in the ground, transferring heat to or from the ground, depending on the mode heat pump is working in. During the summer season heat pump functions as air conditioner extracting the heat from the air inside the […]

Geothermal Equipment

Posted on December 7th, 2010 by admin
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Learn how to choose the right equipment for your geothermal heating systems. Discover which heat pump will work better and serve you longer, how many TONs or BTUs the heat pump should be and what type of geothermal heat exchangers to use. Geothermal Equipment 1. Heat Pump The heat pump itself is the most important part of any geothermal system and is responsible for extracting or rejecting the hot air to/from the ground. The most commonly used unit in geothermal systems is the single package water to air pump which is the size of the small furnace and has all necessary components pre-installed in it. The typical heat pump consists of refrigerant to water heat exchanger, refrigerant piping and control valve, compressor, air coil that […]

Geothermal Heating and Cooling

Posted on September 27th, 2010 by admin
Filed under Geothermal Heating and Cooling | 2 Comments

Geothermal heating and cooling is considered to be the most efficient way to keep you home comfortable. However, very few people actually know what geothermal really is, or how it work, and how much it costs. In this article we will look at basic principles of geothermal system operation and review residential geothermal heating and cooling system operation and installation costs. We will also review the cost of financing a new geothermal systems, compare your monthly payment against the money saved by switching from a conventional HVAC to geothermal. Basic principles of geothermal heating and cooling system operation: A geothermal heat pump system uses the ground you already own to heat and cool your home for less. Geothermal works by using the difference in temperature […]