GB2541634A

GB2541634A - Device for local ventilation with recovery of heat and humidity

Info

Publication number: GB2541634A
Application number: GB1501652.0A
Authority: GB
Inventors: Mitev Gancho
Original assignee: DIMITAR MITEV; MULTINATIONAL EDUCATIONAL CENTER OF BIRMINGHAM
Current assignee: DIMITAR MITEV; MULTINATIONAL EDUCATIONAL CENTER OF BIRMINGHAM
Priority date: 2015-02-02
Filing date: 2015-02-02
Publication date: 2017-03-01
Also published as: GB201501652D0

Abstract

A heat and humidity recovery ventilation device comprises two channels, each having a heat accumulator (heat store) 15, 16 and a flow directing means (valve) 1 alternating air flow through each channel in a supply or exhaust mode thereby charging or discharging heat to / from each accumulator. The device may be formed in a window and comprise internal 12 and external room parts 13, with the accumulators in the external part and the flow directing means in the internal part. Internal 2 and external 3 fans respectively exhaust stale and supply fresh air. An internal valve 7 at an inlet of the internal fan and an external valve 8 at an outlet of the external fan along with rotatable jalousies (louvers, 17, fig 4) controls air flow through the device. Internal 11 and external 12 temperature sensors along with the flow directing means determine which channel is in the supply or exhaust mode. The accumulators comprise a tray (19) having a bottom covered with a thermally insulated net/mesh (18) and houses a metal pipe (25, fig 7) sealed at both ends and containing a low freezing fluid, and the pipe enclosed in two layers of metal wool (26).

Description

Title: Device for local ventilation with recovery of heat and humidity Field

The invention is ventilation system for preservation and recovery of humidity and heat between exhausted and supplied air. European classification - F24F12.

Background

Modern aluminium and uPVC windows provide almost hermetic insulation against cold, noise, and outside dust but, as a result, deprive us of fresh air. In large office buildings and residential estates this problem is solved via central ventilation. However, the issue remains unresolved for individual apartments, houses, offices, many classrooms and generally older buildings where central ventilation is not available and impossible to install. An average adult exudes 30-50g of water per hour (through breathing and perspiration) thus increasing the humidity of the room they are present. The most common approach to maintaining the appropriate level of moisture the in air in this case is to install a dehumidifier. However, this method of humidity control deprives the room of any fresh air supply. Over a prolonged period of time this reduces oxygen levels and increases the amount of G02 thus considerably increasing the risk of respiratory problems.

On the other hand, air conditioners present an interesting conundrum. They create a sense of “illusionary freshness”. As a result, many of their owners see them as a type of ventilation. However, most people are unaware of the fact the only thing flowing through the little pipes connecting the outer and inner body of their AirCon is Freon, and no fresh air actually enters the room.

In modern buildings with wall insulation, uPVC and 4S windows, about 66% of heat losses are caused by ventilation - removing the stale air from the room (i.e. “airing"). To comply with energy efficiency standards ventilation systems are required to recover heat from the exhausted air. Commonly, this is achieved by local ventiiaiion systems that use recuperative heat exchangers with cross flow of air. in spite of their high efficiency, these devices have a considerable disadvantage ~ their working temperature Is restricted to -5 °C (when heat recuperation is highly necessary) because anything iower causes water vapour to condensate and freeze in the heat exchanger as the exhausted air cools down. The ice, in turn, blocks the pathways for heat-exchange thus inhibiting the operation of the unit. There are devices that Integrate a freezing protection mechanism, however. It dramatically reduces their efficiency. Additlonaily, the process of heating up the supplied fresh air (as part of the freezing protection), significantly decreases its relative humidity drops and fosters feelings of “dryness” and discomfort. Consequently, air humidifiers are installed to manage the room humidity. As a result, the amount of energy consumed to support the total ventilation process (ventilation, freeze protection and air humidification) is considerably larger than the amount recuperated in the heat exchanger

Under normal working conditions, the temperature of the incoming fresh air is controlled by the settings of the heat-exchanger and the ventilator. For example, at room temperature of +22°C and external temperature 0°C, the fresh air coming in should not be under 18.5°C.

The efficiency of thermal exchange (η) of a heat recovery ventilation (HRV) system is the ratio between the real (AT(real)) and theoretical (AT(theoretical)) temperature differentials of the air at the inlet and the outlet. AT(real) = T(air supplied) - T(outside air) ΔΤ (theoretical) = T (inside air) - T (outside air) η = ΔΤ (real) / ΔΤ (theoretical) = = [T (air supplied) - T (outside air)] / [T (inside air) - T (outside air)]

For example, if the outside air temperature is 0°C and the air temperature in the room is +22°C then the temperature of the air supplied to the house will be:

ΔΤ (theoretical) = T (inside air) - T (outside air) = 22 - (0) = 22°C ΔΤ (real) = η x (ΔΤ (theoretical)) = η x 22, i.e. T (air supplied) = η x 22 + T (outside air)

In this situation a device with efficiency η = 50% will supply air with temperature equal to:

T (air supplied) = 0.5 x 22 + (0) = 11°C

The air supplied is colder than the one in the house.

Alternatively, a device with efficiency η = 92% such as the “Promote HR 400” will supply air with temperature: T (air supplied) = 0.92 x 22 + (0) = 20.24°C (1)

However, it is of note that a considerable part of the energy of the exhausted air is in fact the “hidden heat of evaporation” of the water in the air. Most recuperators, such as the “Prometeo HR 400”, lose this energy as they discard the humidity together with the exhausted air while supplying fresh but dry air. To restore the humidity levels humidifiers must be utilised. This, in turn, increases the total energy consumption of the space (room/house).

For example, the air in a room air temperature T=22°C and relative humidity of 60%, 12.1 g/m^ of water that is being lost (exhausted). Meanwhile, the fresh air outside has T=0°C, and the same relative humidity of 60%, but contains only 1.9 g/m^ of water. Therefore, 10.2g of water have to be evaporated in every cubic meter of air in that room in order to prevent a feeling of “dryness”. If the air flow is 60m^/h this equals to 0.6 kg of water that have to be heated and evaporated every hour.

If we were to calculate the energy required to: • heat up the 0.6kg of water Q1=m*c*At =[kg]*[ J/(kg*K)]*[°C] = 0.6*4,184*(100°C -10°C) = 226,000( J) • evaporate the 0.6kg of water Q2=m*r(J/kg)=0.6*2.26*10®(J)=1.356*10® = 1,356,000(J)

Therefore, Q=Q1+02=226,000+1,356,000 = 1,582,000 J of energy are required in total.

To put this figure into perspective, a 440W source of power will have to work nonstop in order to evaporate 10.2g of water for every cubic meter of air supplied.

Meanwhile, the savings from a heat-exchanging recuperator with η = 92% and flow of 60 m% constitute: Q= V*Energy*At = [m"]*[J/ m"C]*[°C]= 60*1,300*(20.24 - 0)= 1 578 720( J) (20.24 is referring to calculation (1) above)

This is almost equal to the energy consumed to humidify the dry air brought in. Therefore, the “high efficiency” of most recuperators (such as the Prometeo HR 400) is somewhat misleading. Consequently, one should be aware of the difference between the concept of “thermal efficiency” versus the one of “energy efficiency”, in order to appreciate that the true energy efficiency, or enthalpy efficiency, of such recuperators is actually less than 50%.

The process of heat transfer is more efficient in heat regenerators than in recuperative heat exchangers. Additionally, heat regenerators are structurally simpler and consequently more reliable than the standard recuperators. As a result, devices using heat regenerators are better suited to work at higher temperature differences between inside and outside air: when heat recovery is indeed necessary.

State of the Art

The following patents related to ventilation systems for heat and humidity recovery between the exhausted and supplied fresh air were discovered during the research of our team: • DE 29801917 U1, 20.05.1998 • DE 9301812 U1,24.06.1993

In the workings of DE 29801917 U1, the process of discarding the inside air and supplying fresh one takes place through a single ventilation channel connecting the “inside” and the “outside”. This channel houses a “heat accumulator”, reversible axial fan and a filter. The overall ventilation system encompasses two such devices located either in different rooms or in different parts of the same room and working in opposite directions - while one exhausts air the other supplies fresh one. Both devices are connected to a common electric controller that manages their fan speeds, which once set remain equal and constant for both devices.

The controlling algorithm of the aforementioned ventilation system simultaneously turns on the fans of both devices in opposite directions. After a given period of time the direction of air flow is reversed (rotation direction of the axial fans is reversed).

As a result, the heat accumulator of the device used to discard air, which has been collecting the heat and humidity of the air exhausted so far, starts releasing its heat and humidity to the fresh air supplied and hence returning it to the room.

The existing devices (and patents) described above have the following shortcomings: - the overall supply of new fresh air is limited (between 13 and 40 m%) due to the cyclical change in the rotation direction of the axial fans; - the installation of this device requires the provision of 2 holes in the walls which constitutes a sizeable inconvenience and investment on behalf of the end user; - the device’s heat accumulator has limited volume which restricts the error margin when choosing the size of the holes in the wall; - the energy efficiency drops considerably for flows larger than 20m^/h; - noises caused by the frequent starting and stopping of the axial fans could be considered irritating; - new wiring is required to connect, control and supply electricity to both devices. This may turn out to be difficult or cumbersome for installation especially if the devices are located in different rooms. In addition, this may hinder the user-friendliness of the system; - the devices must be installed in holes in the walls, which might be difficult, unsuitable for certain spaces and might obstruct the optimal placement of the devices. The optimal placement is considered to be near the ceiling so as to allow the tepid air to sink slowly without creating the sensation of a draft. However, this is not always possible due to structural specifics of the building in question (cannot drill supporting columns/walls). Consequently, a suboptimal location is usually chosen. - Gusts of wind can cause significant pressure differences especially for multistorey buildings. This leads to a change in speed of the axial fans, and even to change of their direction. As a result, the ratio of exhausted and fresh air becomes disproportionate, and hence the efficiency of the system falls. In high winds one might even have to turn off the unit.

The disadvantages listed above considerably decrease the customer utility achieved by the existing heat recovery ventilation (HRV) systems, which is one of the reasons for the technology to still remain unpopular.

Statement of Invention

To address and eliminate the aforementioned disadvantages, the present invention proposes a ventilation unit for local ventilation with recovery of both heat and humidity.

The air supply and exhaustion are performed by the inversion of the air flows through two ventilating channels with heat accumulators therein that are combined into one housing.

It satisfies the requirements of the German Energy Saving Ordinance (EnEV).

Saving some 19.5 kWh/m^ on air conditioning per year, the device is also appropriate for buildings of low-energy standards and even in “Passivhaus”. A detailed description of the invention is presented hereafter with references to the accompanying drawings: • Figure 1 - general drawing of the ventilation unit. The invention illustrated in this drawing is housed a plastic body made up of two functionally distinct parts - an internal part (12) and an external part (13), which are respectively located inside and outside the room/space. The internal part (12) houses all elements necessary to create and direct the air flow. The external part (13) constitutes two permeable to air heat accumulators (15 & 16), heat insulation (14) and closing and guiding jalousies (17). The light weight of the unit allows for its installation without additional reinforcement of the windows. • Figure 2 - section of the internal part of the ventilation unit. This part of the invention includes the internal body which houses: o a valve for directing air flows (1); ο a turbine fan (2) used to expel/exhaust the stale air o a turbine fan (3) used to supply fresh air o openings in the rear wall (5 & 6); o partitions (4) that, together with the valve (1) and the openings in the rear wall (5, 6) form the air flow pathway; o a valve (7) at the inlet of the turbine fan (2); o a valve (8) at the outlet of turbine fan (3); o a standard particle filter placed after valve (7) at the inlet of turbine fan (2); o a temperature measurement sensor for the exhausted air (10); o a temperature measurement sensor for the supplied air (11); o valve (1 )’s position (G1), in which stale air from the room is discharged by fan turbine (2) through the opening in the rear wall (6) and the heat accumulator (15), while the fresh air enters through the heat accumulator (16), opening the rear wall (5) and turbine fan (3). • Figure 3 - section of the internal part of the ventilation unit. Valve (1) is in position G2. In this situation the stale air from the room is discharged by the fan turbine (2) through the opening in the rear wall (5) and the heat accumulator (16), while the fresh air enters through the heat accumulator (15), opening in the rear wall (6), and turbine fan (3). • Figure 4 - section of one of the permeabie to air heat-accumulating regenerators. This includes: o Closing and directing jalousies (17) o Standard particle filter (22) o Tray (19) whose bottom is covered by an insulation net/mesh (18); o insulation (20) o “Catechin” filter (21) - a powerful natural antiseptic. It provides a high degree of air purification. Affects viruses by destroying their cell membrane and disrupting their ability to bind to cells and cause diseases. Air that passes through the filter is effectively free of dust, viruses, smoke and other common air pollutants. • Figure 5 - view of the external part of the invention: closing and directing jalousies (17) o Electrically controlled and adjustable - from a closed state to 45 degrees • Figure 6 - a tray (19) of the illustrated shape and a bottom of insulation net/mesh (18).

This is the key module of permeable to air heat-accumulating regenerator.

The tray (19) has a section (24) and dimensions allowing it to be fully inserted into the body of the heat accumulator. It is deep enough to accommodate a “refill” (23). The insulation net/mesh (18) prevents heat losses resulting from heat transfer along the length of the heat accumulator. It isolates separate modules from the heat accumulator and ensures heat transfer solely by convection from and to the passing air. • Figure 7: “refill clip” (23) used in tray (19) illustrated on Figure 6.

The bottom of the tray (19) is covered with an insulating web/net (18). The tray (19) houses a metal pipe (25) that is enclosed between two layers of "metal wool" (26), sealed at both ends and filled with a fluid with a low freezing temperature. The layers of "metal wool" (26) are pressed and / or welded to the metal pipe (25) so as to tightly envelop it and ensure thermal contact.

Everything is placed in tray (19) and constitutes the permeable to air heat-accumulating regenerator. The illustrated structure and design optimises the heat capacity and "speed of charging" of the heat accumulator.

The invention will be controlled via an electric block with switches allowing for the use of a remote control. This, however, is not part of the current invention.

Detailed Description

The present invention meets its objective, as detailed above, by adding the following elements to existing ventilation units (all reference numbers below are used across all figures outlined above): o a valve for directing air flows (1); o a turbine fan (2) used to expel/exhaust the stale air, with option to regulate the overall flow; o a turbine fan (3) used to supply fresh air, with option to regulate the overall flow; o openings in the rear wall, which, along with valve (1) constitute the air flow pathway (5 & 6); o a valve (7) at the inlet of the turbine fan (2); o a valve (8) at the outlet of turbine fan for admitting fresh air (3); o a temperature measurement sensor for the exhausted air (10) and a temperature measurement sensor for the supplied air (11) that compare the temperature difference between the supplied and exhausted air. Upon reaching the pre-set difference they send a signal to the valve for guiding the air flows to be turned from G1 to G2 (or vice versa) (see Figure 2 and Figure 3) o a remote control for convenience

The device measures and compares the temperatures between the incoming fresh air and the exhausted air. It uses this data in order to determine whether speed 1, 2 or 3 (which can be different for each of the turbine fans) is necessary to ensure the optimal parameters, such as temperature and humidity, for each room.

Therefore, this unit constitutes a device for local ventilation with recovery of heat and humidity with a stationary heath regenerator. This is a ventilation device for a continuous local air-exchange including a built-in high-efficiency regenerator with a heat accumulator whose parameters for “thermal capacity” and “speed of charging” have been optimised to deliver maximum efficiency.

It can provide noiseless and continuous ventilation of the house thus removing the stale air that is being discarded from the house by one of the two noiseless turbine fans with very low power consumption. The heat and humidity of the exhausted air are stored in the installed highly efficient regenerator, and are subsequently passed on to the incoming fresh air. This allows for an energy efficiency coefficient of over 90% to be achieved.

Partial humidity retention in the air could prevent dry air and improve comfort. What is more, it protects the regenerator from freezing in low outdoor temperatures.

The invention uses two low-noise turbines with permanent rotation direction, thus avoiding the cyclical way of working observed in the existing solution (described in the Background section). The inversion of the air flow direction through the two ventilation channels (5) and the heat accumulator (6) is controlled via a central electrically driven valve for directing airflows (1).

The combination of the above-mentioned elements and functions that characterise the ventilation device proposed, is absent in any available sources.

The invention creates new opportunities for consumer utility and eliminates the disadvantages observed in existing systems.

The key characteristics of the invention are: • high level of efficiency that is not disrupted by either a continuous and uninterrupted operations or overall air flows of over 80m^/h • continuous air supply through the valve (8) and continuous discharge of the stale air from the room through valve (7) • uninterrupted operation of the axial fans, which usually causes noise and consequently discomfort to the user • ability to function in strong wind • ease of installation and use

The benefits listed above constitute the innovative and useful elements of the invention.

Examples and versions of the Invention

Example Nq1

In this example of the invention „Device for local ventilation with recovery of heat and humidity” the device is modeled with specific dimensions such as to fit the small window to the balcony. The window is removed and the unit is installed in its place.

Operation of the ventilation unit illustrated on Figure 2.

In ‘off’ position the valves (7) and (8) are closed. The closing and directing jalousies (17) of the two regenerators also are closed. The valve directing the air flows (1) is situated in position (G1).

Upon switching on: - Valves (7) and (8) and the jalousies (17) open; - The turbine fan (2) and heat accumulator behind it (15) start to discharge stale air from the room through the openings in the rear wall (6). The heat accumulator-generator (15) behind opening (6) absorbs warmth and moisture from the air; - Turbine fan (3) and heat accumulator (16) begin to introduce fresh air from the room through the openings in the rear wall (5); - After a given unit of time, or upon a signal from the sensors, the valve directing the air flows (1) turns to position (G2); -Turbine fan (2) continues to discharge stale air from the room, but through an opening in the rear wall (5) and the heat accumulator behind. The heat accumulator behind opening (5) absorbs heat and humidity from the discharged air. - Turbine ventilator (3) continues to supply fresh air from the environment but through opening in the back wall (6) and the heat accumulator behind it. The heat accumulator behind opening (6) emits the heat absorbed to the incoming fresh air.

Upon a signal from the thermal sensors, the electrical unit switches the valve for guiding the airflows (1) into position (G1) and the process is repeated.

The high efficiency of the ventilation unit proposed is due to the fact that it is “enthalpic”, i.e. between the incoming and outgoing air flow humidity is also being transferred.

The ventilation unit is efficient not only during the winter, but also during the summer. When operating alongside an air-conditioner, it keeps the coolness in the room and saves the 440W cooling energy that would be used for “drying” the fresh air supplied.

Upon switching off: - Valves (7) and (8) and the closing and directing jalousies (17) close; - Valve for directing the air flows (1) takes position (G1)

When the device is in working mode the process repeats continuously.

One of the airflows cools as it heats the regenerator. The humidity in it condensates and/or freezes and emits to the regenerator the “hidden heat of the evaporation”. The moisture evaporates and enters into the room upon the subsequent passing of fresh and cooler dry air in the opposite direction. Not only does this maintain the temperature but also adds an appropriate amount of humidity to maintain the comfort in a room.

The turbine fan rotation speed and the productivity of the ventilation unit are determined by the users.

During the process of removing the air, the relative regenerator is warmed up. Then, in the process of inflow - the temperature of the air brought in gradually falls down. The dimensions, process duration and productivity of the turbine fans of the „Device for local ventilation with recovery of heat and humidity” are selected so that under normal operation of the ventilation unit the temperature of the fresh air always remain over the minimum allowable - determined also by the user.

The changes in the external air pressure caused by the wrapping of buildings during gusty winds do not affect the operation of the device, as it does not use axial fans.

The specification and design of the „Device for local ventilation with recovery of heat and humidity” device allow each of the enlisted working modes, which cannot be achieved with previous models.

The invention is a good technical solution as it is based on testing and analysis of previous models and It is ready to manufacture.

Example Nq2

In this example of „Device for local ventilation with recovery of heat and humidity” performance, the glass of a selected window is removed. The device is installed at the upper side of the window. Afterwards, a smaller glass is installed in the remaining opening. A tight mounting is achieved due to the built-in within the ventilation device box - Figure 1 - underneath and right between the internal part (1) and external part (2) profile for window of PVC joinery. The device’s low weight allows for its installation without further reinforcement of the window pane.

The ventilation device operates as described in above in Example 1.

Application of the Invention

The „Device for local ventilation with recovery of heat and humidity” can be manufactured and mass-produced at an assembly line for producing internal bodies of “split-system” air-conditioners. The installation can be undertaken by joinery fitters. The product is user-friendly and has major benefits as outlined in the sections above. A professional specialising in the area can easily accept many modifications of the invention, described in more details above. This is the reason why the applicant intends to only restrict their involvement to the reach of the proposed dimensions.

Claims

1. A device for local ventilation with recovery of heat and humidity that supplies and discharges air by inverting air flows through two ventilating channels with heat accumulators (15) in each one.

2. A device according to claim 1 characterised by two openings at the rear walls (5) and (6) with heat accumulators (15) and (16) in each one, housed by one body

3. A device according to claim 1 where the inversion the airflows through both ventilation channels is realized by a dedicated valve (1) which directs the air flow (Figure2):

4. A device according to claim 1 where air flows continuously through valve (8) and valve (7) without change of direction (Figure2);

5. A device according to claim 1 where the heat accumulators (15 and 16) constitute a metal tube fixed between two layers of “metal wool” (26) sealed on both sides and full of liquid with low freezing temperature (fixed as shown in figure 6);

6. A device according to claim 5 where the two layers of “metal wool” (26) are pressed and/or welded to the tube so that they provide thermal contact;