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The application of air source heat pump assisting solar low temperature floor heating system in the construction of new countryside Cao Hui Liao Qiuyang Department of Urban Construction of Yangtze University in JingZhou HuBei 434034 Abstract It introduces the advantages of solar energy the characteristics of low temperature radiant floor heating system as well as air source heat pump s helping role in the application of solar energy It expounds that the air source heat pump s auxiliary function will be comparatively weakened energy efficiency will be lower if it works under low temperature conditions We should pay special attention to the quality of the heating coil in the installation process The air source heat pump s helping role in the application of solar low temperature floor heating system has been an an effective way of energy saving and emission reduction in the new countryside construction Keywords crackage solar air source heat pump and application As the populaition is scattered most rural areas in north China vast havn t adopted any concentrated heating system Most residents there tend to use coal wood platycodon grandiflorumand other materials to keep them warm The disadvantages are obvious it makes the indoor temperature uneven the quality of the air indoors is much poorer than outdoors 1 As the new countryside construction is marching all over the country the peasants living mode has changed from scattered to centralized The local governments construct a large quantity of housing districts where the peasants can move into the uniform unit buildings and live concentrated Their living conditions have been improved to much degree However at the same time the task of energy saving and emission reduction in these buildings seems to be urgent Under the heavy pressures of energy crisis and environmental pollution solar energy clean and renewable has been warmly hugged by people At present solar buildings are being built all over the country In order to make the most use of renewable energy and make the application of solar energy a priority solar heating system accompanied by air source heat pump has turned to be the best choicein the new countryside construction 1 The advantages of taking solar energy as heat source As it known to all solar energy is a kind of inexhaustible and renewable energy Nowadays energy has still been in great demand Energy problem has become a big probem for many countries So the renewable energy has been paid much attention and will surely have great potential Our country is rich in solar energy resources and the annual storage volume can theoretically be equivalent to 1 7 trillion tons of coal Therefore in the construction of new countryside taking solar energy as the heat energy of heating system is an important means and method of energy saving and emission reduction 2 The characteristics of low temperature radiant floor heating system 2 1 Why it is difficult to promote it in our country Low temperature radiant floor heating is not a new technology At the beginning of 20th century many foreign countries had applied it into in engineering projects However because the metal pipes are easy to have corrosion and leakage which is very difficult to solve this kind of heating system fails to develop rapidly Until 1970s with the technological development of plastic instead of steel and the appearance of polyethylene pipe the low temperature hot water floor radiant heating system had been given a new life 1 In our country low temperature floor radiant heating system as one kind of heating system is gradually adopted only in recent years 978 1 4244 9577 1 11 26 00 2011 IEEE There may be two reasons for this phenomenon for one reason our traditional heating means is convection radiator heating for another people in China mainly live in apartment style buildings where the metal pipes have been laid in the floor If they choose low temperature radiant floor heating system the metal pipes won t last long and it is not easy to mend it 2 2 The advantages of low temperature floor radiant heating system 2 2 1 It can use low heat source In most cases 40 50 C can meet the demands of low temperature radiant floor while the traditional convection heating always need to boil the water to high temperatures As a result it can save energy and protect our environment And the application of solar energy in low temperature radiant floor heating system will with no doubt be the best low heat source It is significant and can meet the demand of energy saving and emission reduction nowadays 2 2 2 It is comfortable beautiful and will not occupy usable room The traditional radiator heating system is often installed on the middle and upper places of the room Therefore the heat decreases from the ceiling to the floor People are easy to feel thirsty and uncomfortable However the low temperature radiant floor heating system can send out the heat evenly through the radiation means The radiant heating system is the most comfortable heating means It can keep the temperature on the ground even Also as the temperature gradually decreases from the floor to the ceiling it keeps the feet warm and the head cool which makes people feel good It can improve people s blood circulation and promote metabolism 2 What s more radiator heating system mainly relies on natural convection mode Because the temperature of the heat source is high the air indoors flows fast Floor heating system mainly relies on two ways radiation and natural convection It also uses heat medium of lower temperatures In this way it avoids the strong convection of air indoors As the air indoors flows slowly it prevents the dust from flying and greatly reduces the air secondary pollution caused by convection Because wind speed is an important factor of blowing dust the room equipped with floor heating will raise little dust which keeps the room clean Therefore the floor heating system can improves the home environment All sorts of pipes and lines indoors can be laid in floor heating structures and there have been no standpipes and branchpipes of radiator indoors Not only will it increase the usable room but also makes it convenient to divided rooms which is good for furniture facilitating and room decoration 2 2 3 It is effective in heat preservation and sound insulation and its heat stability is good At present we commonly use precastslabs site casting slabs as partition floorslabs As their textures are friable and hard the effect of sound insulation is very poor When someone walks upstairs people downstairs will be disturbed by the noises Because the floor heating system owns insulation layer it can greatly reduce the noises made by the upstairs and is effective in sound insulation The floor heating is special in structures Even if the upper and the lower floors are not heating the middle floor will not be affected As the ground layer and the concrete layer have large storage of heat the temperature indoors will change slowly even when the heating system works in the intermissions Therefore the heat stability is good Floor radiant heating system with thicker concrete and mortar layer as its heat storage structures has strong ability of heat storage So its thermal lag is stronger and has a good heat stability which is also strong enough to resist interference Consequently even if the heating system works in the intermissions the temperature indoors won t change too much 3 The auxiliary application of air source heat pump technology Heat pump technology is an effective way of reducing greenhouse gases The world s heating and hot water almost come from burning fossil fuels Therefore The emission of carbon dioxide accounts for nearly 30 of the world s total quantity Air source heat pump absorbs the low temperature heat source in the air and can add up the temperature of the water when it is changed into high temperature heat source through compressor The application of solar energy is easy to be influenced by the weather When the weather condition is unfavorable or the area of placing the collector on the roof is finite we can only rely on other auxiliary heat source The air source heat pump has several advantages it is effective in energy saving it has no emission the cold and hot heat source are combined it is more comfortable high and it is safe and reliable So it has become first choice to remedy the defect of solar energy 3 At present The technology conditions of residential air source heat pump s application in auxiliary solar water heating system GB T 23889 2009 has approved by the relevant state departments It has been announced to the public on June 1 2009 and carried out on Juanuary 1 2010 This standard emphasises that air source heat pump be placed in auxiliary position in the combined system It must be in accordance with the original national standards of heat pump and must satisfy the normal operations of the solar water heating system at the same time 4 4 The problems at present 4 1 Low temperature s influence on the operation of air source heat pump The low temperature outdoors is the most important factor of the coefficient of performance With air temperature outdoors decreases the refrigerant s inspiratory hematocrit increases and the unit s inspiratory quantity decreases At the same time the quantity of heat drops However it is just the summit of heat demand of the end users The unit cannot meet the demand of them Meanwhile the compressor s compression ratio increases continuously and the temperature of exhausted gases increases rapidly When the temperature exceeds the set point the compressor will change into downtime protection condition to prevent overheating In addition it may damage the equipment if it exaustes gases under high temperature for a long time Therefore we should take the local weather conditions into consideration When the local weather is extremely cold we can choose heat pump units that is suitable for low temperature or add electric auxiliary heating facilities 4 2 Radiant floor heating problems that should be paid attention to in the construction Radiant floor heating is a project of concealment It is poor in maintainance Once there is leakage in the pipe it will be difficult to repair it It needs professional equipments to check the leakage and repair it The plastic pipe has several advantages it has no joint it is easily bent it is easy to use in the construction So we often choose plastic pipe in the construction The commonly used plastic pipes are crosslinked polyethylene polypropylene PP PEX tube modification C tube polybutylene PB tube crosslinked polyethylene aluminous model fits the tube they have XPAP They are anti aging corrosion resistant not fouling anti pressure environmentally anti leakage water resistant and has small expansion coefficient What s more it can last for 50 years under the environment of 50 No matter what kind of pipes we choose there are some requirements the inside and outside of the materials should be flat and smooth it must be without bleb split crack peeling apparent scar grain and concave the color of the materials should be consistent and even it should be handled and put down carefully when you load and unload it it cannot be collided violently it cannot cast fall roll and drag it should avoid contact with grease we should prevent mud and other things into the pipes during the storage and construction processes the pipes should avoid direct sunlight 5 6 5 Conclusion In the new situation more and more farmers have moved into unit buildings However it is un practical to adopt regional concentrated boiler heating system like small towns which may